I'm confused. Option A is "idyllic Magical Aura" in a "null Aura location"? That's contradictory. And I'm not sure why all these things showed up for "B in a null Aura." Did you change your labeling in the middle?
Now, for comparison. First, I don't think Aura +7 is very average. I don't think I've ever played with an Aura that high. Is that really fairly average in your games, or are you choosing something rather extreme to be representative of typical? This is why I was working off an Aura of 5. 5 may be a little over average, but it seems to be pretty popular.
So, with an Aura of 5 v. an Aura of 0, what could we do? 2 seasons setting up our labs leaves us with something useful in either case. Now we'll also note that we could do something like take Inferior Equipment along with Spacious in the Aura 5 lab during those same 2 seasons. Let's say we do that. Our 5-Aura lab is at +2 botch dice due to Aura and Safety +3, and has +4 to all work due to Aura and General Quality -1.
You proposed 2 more seasons of work as acceptable for our young mage, so I'll use your suggested 2 seasons:
- No aura: Major Focus/Feature for experimentation (since that's the goal).
- +5 Aura: Refinement +1, Superior Tools, Minor Focus/Feature for experimentation.
Let's compare these two labs that are both done fairly early in the career, looking at the particulars:
- No Aura: Aura 0, General Quality -2, Experimentation +7
- +5 Aura: Aura 5, General Quality -2, Experimentation +3, Safety +5
So after your two suggested seasons my more typical-aura lab has the same botch dice as yours but gets me +1 more toward experimentation.
Now let's look related bits as well. If we started with labs at the covenant, this process takes fewer seasons for mine. With one more season I can upgrade to Major Feature/Focus, upgrading faster than the other lab can be done. When I get a Gold Cord, I have things I can sacrifice to give up excess Safety in return for the things I want. So it's likely I can hit this superior point faster, and I can improve faster from it as well.
(Now, personally, I'd actually have other people setting most things up, and I really prefer multiple small labs. But most people don't seem to do things these ways, so I didn't bother delving into that.)