Ok, so munchkin?
en.wikipedia.org/wiki/GNS_Theory
ArsMag is not gamist: a saga is narrative by nature, using History is simulationist. Is it because you are going down the gamist path that we talk at cross purpose?
As for the answer, that's what I tell myself every time I wonder which way to go
Um... This has nothing to do with whether the game itself is gamist or not. Believe me, I know that it's not. I think you're missing the point that a discussion about mechanics is a discussion about mechanics. Just because I want to stay on-topic with the thread doesn't make me some powergaming munchkin who only cares about roleplay as it relates to gaining mechanical advantage. Mechanics are just what's being talked about, and I'm trying to talk about it without diverting the topic into areas that aren't relevant... Like, say, how much fun you can have regardless of power. I'm pretty sure even the concept of fun isn't being discussed right now. Sure, that's a bit misaligned with the entire philosophy of Ars Magica, but that doesn't change that it's the topic at hand. I really don't see where you're drawing your conclusions about my gaming thought process from.
No, just not subjectively judgemental.
"Fun" is purely up to the individual. Weighing the advantages (or relative lack of them) of virtues can be less subjective.
Ok, now I understand... I think. It's the gamist/simulationist POV: how to have fun doing things, rolling dice, advancing characters.
For instance, spontaneous spells are "less fun" because you have to calculate it on the fly, whereas formulaic are ready to use. Or formulaic are "less fun" because you have to plan ahead. Or having a focus makes it easier to think about which spells to invent. Close enough, I hope?
{I should have said "power-gamer" or "gamist" instead of "munchkin" 
}
I think the point is not about fun, but rather a "thought experiment" as to what Virtues and Flaws might be considered better or worse, from a merely mechanical point of view. I think we all agree that in the end, what makes a Virtue of Flaw better when actually playing with a troupe will be more a function of the troupe's interests, style of SG'ing and a mixture of mechanics and story potential.
But, and please do correct me if I'm wrong, as far as I understand it, this thread is just about the mechanical point of view. I'd consider it more of an analysis of the mechanics of the game, than a discussion about what V&F would be best when actually playing, since that mostly depends on the people you play with and the style you enjoy the best. And, as a purely mechanical analysis, it can be quite helpful when making decissions during actual gameplay, even if what's "best" from a mechanical standpoint is not what actually "best" at your gaming table.
I mean the above explanation not as an authoritative assessment of what this topic is about, nor as a demeaning comment on anybody's posts. I aim just at helping get us on the same page as far as what the thread's topic is about. 
I mostly like 'active' Virtues - things where you need to do something for them to be of any use. Like Fast-Caster or Second Sight.
I find the totally passive Virtues more boring - like the Exp boosters, or things that add a bonus to things. Although they are very handy sometimes.
For an exception to this I need to mention Independent Study (HoH: MC - Merinita). Although it is also an exp booster, I find the fact that it adds Story Exp per story motivates characters to go out more. We all know the reclusive Verditius lab rat who rarey if ever ventures out. Also, it brings the Source Quality of Practice almost into the range of competing with other study methods, so IMHO it opens up for more variations, giving the opportunity to learn something for which there are no books or teachers. Great for learning Nature Lore for instance.
You can really only answer what is the best virtue for the character, troupe, saga, and view it holistically, IMO.
If you're going to be in a short running saga, all of the XP virtues (Educated, Warrior, Skilled Parens) are really powerful. If you're in a long running saga, Book Learner will blow those virtues away in 16 seasons of book study, which is how a magus primarily advances. Then again, Book Learner only works on the books you have (at Covenant creation) or the books you acquire (through stories or expending vis/silver), so it can be inflexible. For example, if I pick Educated as a virtue, I now have 50 xp I can spend on something else, because it gets me to Latin 4, which I needed as a magus anyway.
I don't think there is a same page possible here.
That, sir, is very very true.
Still, I think there is something to be gained from analyzing the relative merit of several Virtues and Flaws, as has been (and is being) done here, since it will at the very least help a Storyguide gauge the impact of different Virtues and Flaws, and thus help players selecting them during character creation.
Edited for typos.
A character is more than the sum of his parts.
I have a maga with the following:
Virtues: The Gift (0), Hermetic Magus (0), Self-Confident (0); Gossip (1); Independent Study (1); Major Magical Focus (weather) (3); Affinity with Auram (1); Puissant Auram (1) Life Boost (1); Fast Caster (1); Skilled Parens (1)
Flaws:
Chaotic Magic (3); Carefree (1); Poor Concentration (1); Busybody (1); Plagued by Supernatural Entity (Ukko) (3);, Master of None (1)
It says a lot about her, about who she is, but it doesn't say everything. You don't know her age, what her scores were at when she gauntleted. It doesn't say what House she's from.
Mechanically, it tells you she's a weather maga, and can probably fling lightning bolts, given her focus and affinity/puissant Auram. She can obviously boost the penetration with Life Boost, she's fast, and had a parens with a high teaching SQ. 
She rarely casts spontaneous magic, her weather spells are difficult to maintain due to poor concentration (which reinforces her as a Lightning flinger). The entity plaguing her, you don't know about, and you know she can't focus on one Art/Ability more than once per year...
I'd wager she's Tytalus - because she has Self Confident for a cost of 0. Sounds like a House Virtue to me.
But you're right. You'd need at least a couple of sentences describing her to get any fell for her. In fact, those words would be more useful to me than a list of her V&Fs.
Also, with Independent Study she sounds like she is likely to go out on adventures, and try things by herself rather than sit and flip through books. That particular Virtue is a favourite of mine.
Combo virtues work well. Any multipliers that stack are good here. Focus + diedne magic + chtonic magic + verditius stuff (not sure about these since verditius are my least favourite house)... Anything that multiplies your casting or lab total, really, and keeps multiplying it. the sum in these case is much more than the individual virtues. These add up fast and can achieve high totals with modest starting values. Throw the sacrifices of RoP:I in and you can scale the power level pretty fast. For a small token price.
Xavi
Yup, she's a Tytalus. With a Skilled Parens. There's an interesting story there to justify the combination.
And with regards to Independent Study, when you couple that with Master of None, you get her trying out a lot of new things, and when she does study from books (currently two seasons per year to get her scores up for the LR) she has to study different things, she can't just go all in and study the same book for those two seasons, or spend a year doing study of the same thing unlike her covenant mates. Assigning adventure XP is also something of an exercise...
Why justify? Magi of House Tytalus are superior, as is their training, so Skilled Parens is a natural
I tend to see house Tytalus being likely to produce magi with a weak parens, rather than a strong parens.
But the whole thing was meant to be a more than the sum of her virtues and flaws. Every virtue and flaw is there for a reason and has its own justification or story for it being present.
...not so sure. Tytalan magi spend the apprentice's entire career abusing them 'to make them strong', but all that really results in is the Self Confident virtue. There's no 'extra training' or 'superior teaching' going on here, just making them self-reliant.
Contrast with a Jerbiton apprentice, who might be given to proper tutors for non-magical learning, or a Bjornaer who gains his Heartbeast early and might be able to dictate some of his own studies.
OTOH, being a Tytalan apprentice might mean you pull down Adventure XP EVERY season you're not in training as your pater makes you do dangerous crap. The rules of apprenticeship don't reflect this, however.
slow grin Sorry about omitting the smiley. Societas says that Tytali consider themselves the very best of magi, so I just went along.
I would imagine that some Tytali do end up with a Skilled Parens and some end up with a Flaw.
It got me thinking. I sort of miss 4th edition in the way that it forced XP purchases based on house, and I'm of the opinion that apprentices get a raw deal, XP-wise. I agree that the arts/spell levels is good, but the notion of "apprentice = 3 season lab slave" is pretty unrealistic. Maybe for House Bonisagus (research! research! research!), but even they have seasons where they publish or study.
Let's look at the houses and how apprentices might get more XP than mere exposure:
Bjornaer: apprentices are considered magi after they express their Heartbeast. They still do the 15 years, but it would be grossly inconsistent to call your filius a magus and still treat him as a full on lab-slave 3 seasons of the year. If you're not needed in the lab, your master can arrange for a book or a teacher or even (gasp) some free time to do what you might want, like practicing Heartbeast.
Bonisagus: early on, at least, the faster your apprentice knows Latin and Magic Theory the better. The first few years of a Bonisagus' apprenticeship would be getting Latin to 5 and Magic Theory to 3. After that, yeah, one season of teaching/year and 3 of lab slavery, unless the parens is doing something else, then more reading Magic Theory for the apprentice!
Criamon: Hard to pin down. I don't see a lot of Criamon being hard-core laboratory users, but I can see them dragging apprentices around to gain mystical experiences. Adventure XP might be common for Criamon apprentices.
Ex Misc: Another hard one to pin down. I'd expect more training in the Ex Misc special virtue(s). At the very least I'd expect an apprentice to get more seasons of Practice than in most other houses.
Flambeau: Less focus on Latin/Magic Theory, more focus on practical training. If you're not using the apprentice in the lab, hand him over to the arms-master for training. Make him practice spells for Mastery.
Guernicus: Prospective Quaesitors need a LOT of training. Awareness, Folk Ken, Code of Hermes, Intrigue, Etiquette, Leadership, the list goes on. Not helping in the lab? Here's a Teacher, get learning. I'd expect these guys to have far and away the best training any house would provide.
Jerbiton: Study magic? Sure, we could do that. Or we could visit Paris. Apprentices get a lot of practice in Area Lore and Social Skills as well as adventure XP (social adventures with other Jerbiton apprentices).
Mercere: Apprentices are family - literally. Combine high expectations with familial indulgence. Stir in the necessary skills to perform as a Redcap if need be. Extra teaching necessary, but there are plenty of Redcap volunteers for this.
Merinita: Less focus on Magic Theory, more on Faerie Lore. Probably not a lot of bonus teaching, but some adventure XP dealing with faeries.
Tremere: Apprentices need to be useful to the house. Probably at least one extra season a year of teaching, if not by their pater, by someone else.
Tytalus: enjoy being miserable. Mastering magic is your only hope of escape. Your master gives you seasons of mind-numbing work, during which you do as little as you can get away with and Practice what you can, Read what you can't practice - just as your master planned. Oh, and your pater sends you on terribly dangerous (carefully constructed) adventures to make you strong.
Verditus: Training is the rule of the day. Your pater doesn't need your small contribution to lab total often. While he makes stuff, you get trained in his Craft.
I kind of see the logic there, but personally I'm not a fan of forcing how players spend their xp. (And I would never, no matter what House they chose, force them to have a starting Magic Theory of less than 3. If they don't want to spend the xp that's on them, but I'd never take away the option) And of course, you have to remember that not every member of a House is going to follow the usual rules. Sure, there are general things, especially for Mystery Cults; Faerie stuff for Merinita, crafting for Verditius... I mean, the Magus wouldn't be in the House if they didn't do that stuff. On the other hand, there's an entire section of Bonisagus that cares more about politics than improving Hermetic Theory, and you can expect at the very minimum for different instructors to have different levels of strictness and study allowance regardless of their House. Except Tytalus, again, because their House Virtue is literally based on how grueling their training is, 100% of the time. (Not that this is necessarily a bad thing; I mean, Adventure xp is certainly a better source of training than Magic Theory exposure in the lab, even if it sucks for the apprentice in question.)
There's too much potential teacher variance, and too much concept choice that I wouldn't want to take away from my players. YSMV.
The game already takes away choice. You need Latin 4 to read and a host of very necessary skills (Parma, Finesse, Penetration, Code of Hermes, Magic Theory, Order of Hermes Lore) and you get 240XP to buy it all with - and if you want to be half-decent at anything else, FORGET IT.
My point is that apprentices should have more XP, because it's easy to justify them getting more than 1 season teaching + 3 seasons exposure. Even one extra season a year of learning is in the order of +150xp over the apprenticeship.
Yes and no. I agree that a starting magus is pretty green; having to spend 90 xp out of 240 in Latin 4, Magic Theory 3, Artes Liberales 1 and Parma Magica 1, and 150 xp for everything else doesn't allow for a lot of differentiation. But every magus character is very much the same. So there is choice, every starting magus can spend 150 xp freely as they want, they could even cheat some of the XP from the recommended Magic Theory score of 3 away, but it's not recommended. And if you don't like that, you can age magi a few years, which is pretty standard.
And you can do that, if you want to do all the work that is necessary with the optional rules for Extremely Complex Character Generation. And it is a lot of work. It's almost as if you're playing an apprentice. And yes, apprentices played through apprenticeship will be stronger than one generated by RAW. But so too will a magus 40 years post gauntlet be different if he's played than if he's generated by RAW.