This group of scary scientists practically torture you until you "die" and then you miraculously survive only to find those same people again and you would join them? You would join the bunch of murderers who killed you? I have a bit of a hard time accepting that. Plus, I don't think even Nomura would suggest that these faces we know were tortured to death.
Well, think of it this way:
You're taken in by these scientists who you thought were supposed to be working for the good of your homeworld, stuck in a cage, forceably injected with darkness until your heart collapses, and forced to watch your best friend suffer the same fate.
You somehow manage to come back after all of this, only to find you have no emotions, no goals, no homeworld, and no one you even remember caring about besides that same best friend.
Why would you want to
avoid those scientists? You're not
afraid of them -- you can't be. They could kill you or force more darkness into you -- but who cares at this point? They're the only people you have
any connection to, and even if you can't exactly
hate them, they certainly
deserve to be punished for what they did to you.
So why
not join them? It's not like you have anything better to do, and it's not like you'll feel
bad if you can find some excuse to murder them for what they did to you.
You don't think dying by the hands of scary monsters made of darkness and then being born without ANY emotions wouldn't cause a bit of a personality change?
None of the apprentices changed nearly as much as Isa did, so it can't be
just that. =P
Also, how do you explain Axel aging like ten years in a single year (assuming he is an experiment)? A little iffy there.
Axel didn't age any more than Zexion did, so I'm not sure that's the best argument.