Why should you ever want to have a high Body* when a higher Reflexes* is a better payoff?
For example, Body decreased the damage you get and increases the damage you do, but because the Outcome adds to the damage, then Reflexes both de- and increase the damage as well. In addition, you also get the chance to avoid all the damage with a high value in Reflexes.
So why should anyone put their points in Body?
I'm talking about the primary attributes, but the secondary ones are included as well. Just imagine that you use the secondary ones in the most winning way.
[color=darkblue]Crap. I spent 20 minutes phrasing a response the way I wanted it, then realized I was addressing the wrong question. Siiiiigh. Lack of sleep. Nevermind.
In short, I can't think of a good reason offhand why you'd increase Body in and of itself, unless you happened to have a lot of schticks or skills based off of Body sub-attributes, so that raising the core Body score would be cheaper than raising all the sub-scores individually. But again, I can't think of a PC concept where that would be applicable. So I don't think I know anyone who'd increase Body just by itself.
Higher toughness also decreases damage from other sources, which can be useful. This would seem to be a poor payoff for an increase in Speed, but there are four reasons I can think of:
No amount of messing with Reflexes will increase your combat skill at character creation, so to start with points sunk into Body will usually make you more effective to begin with. Also, when you do this, it will be cheaper to buy up Reflexes (and hence your combat skill) later on.
If your Reflexes is higher than Body, it may be cheaper to buy up Body.
You might be aiming for Ich BIn Ein Bruiser.
You might be a Sorcerer. Reflexes will only impact your Speed, and you can do better than that using Movement magic anyway. Similarly if you're a Ghost, a Taoist Wizard or a Magic Cop who concentrates on Sorcery primarily. I guess if you're a Supernatural Creature who used creature powers- based attacks the same holds true.
What Queex said about Reflexes not doing squat to increase your starting DV definitely qualifies. Barring Fortune Dice, you're only as able to avoid getting hit as your main combat AV, with a +3 increase if you're able to spare a shot or two on Active Dodge. And sooner or later, you're going to get hit, and a shotgun or assault rifle is going to take more out of someone with Body 5 than someone with Body 7 or 8, especially with a high Outcome.
Unless you're a gunslinger or someone specializing in fu powers that don't rely on strength, you're going to need a high Body score in order to deal out the really serious damage to the named guys.
Your Move score, which is how far you can move in a three-shot action, is based on Body, not Reflexes, and has an influence over certain movement schticks such as the wuxia leaping powers of the Leaping Storm.
And Body really helps when it comes to making those Death Checks.
That said, my main high stat when starting characters out is Reflexes for a reason -- you may not be able to increase your DV past your starting max at creation, but in addition to making those other skills reliant on Reflexes (such as Driving, Intrusion or Sabotage) easier to get good ranks in and freeing up some of those points for other skills, a high Reflex score means a high initiative, which can really make a difference in a serious fight, and against the really nasty opponents, you're going to need all the shots you can get.
I've made it a habit to include the occasional Constitution-based obstacle in my adventures--one bout of dealing with tear gas will quickly demonstrate to the party the advantages of a high Body.
In our campaigns there is normally a cap on AV (commonly 14) at start up, and an additional cost (3x or 4x new value) to increase your AV. Characters tend to max out on AV at start up, and then forget all about it. That maxing out can be done with the base skill level + skill level bonuses. If that is the case, the comparison is 'do you want more speed, or more move/strength/toughness'. This seems to result in balance in our starting characters, where some go up the Brick path and some the Speed path.
OK, Queex said it all, but I wanted to pitch in an example: one of my favorite PC is a gentle giant martial artist with Body 10, Reflex 6 and the first 3 shticks of the tiger path. He is an all around nice guy who only fights in self-defense (at no shot cost with his fu shticks), and his high body ensures that he will suffer less damage and deal more damage than his opponent, giving him the higher hand in melee.
From there, it is also cheaper for him to increase his Martial Arts through his reflexes, but increasing his Body to Big bruiser levels also plays to his strength in combat and allows him to race motorcycles or cars for a short time. It is also more fun than straight Martial arts AV inflation.
I think that would be the key for me - regardless of campaign style and house rules - fun. If the player thinks there is fun to be had going down a particular path (e.g. the high Body path) the GM should encourage it. Depending on your game, it might stand alone as a valid thing to do, or else the GM could offer points breaks/house rules to encourage it. I like having a mix of character types in a game, so that different people can shine in different circumstances.
