I've done both, as have most of the professionals in the business, I'd guess.
I'd guess most of us choose "some of both". If you can't have it all at once, you still want stability and to be paid fairly wherever you can be, but you might also want to do a couple of type-B projects if you think they're really special.
But then the real solution would be to find the financial backing or independence to be able to build project B without being at the mercy of someone with poor finances, which can end in tears for a lot more people than just the architect! I think the big players in the business have done this a lot over the years -- recognizing when someone comes to them with a good project but no way to pull it off, and bringing in the pieces that are missing. That solution is not foolproof, either, but at least the designer gets to build it and (usually) gets paid before the problems arise.
If you were trying to take the finances out of it, as in your next to last paragraph, wouldn't everyone want to get to build their own vision? It's just that sometimes sacrifices have to be made to get to do it. I've had more than one designer say to me, "I wish I could build projects your way, but I can't," and usually their holdup is the financial sacrifice involved. I haven't gotten rich doing them my way! (Yet.)