It would have to be Alice, but only because Rosalie's motivations are so foreign to me. I just can't see the profit in holding a grudge for freaking centuries, and being nasty about it the whole time.
I really don't understand Alice's motivations either, but her actions aren't usually hurtful by intent, and she was very kind to Bella when Bella needed a friend.
Well, also there's the fact that Jaz would be my mate, and that outweighs a whole lotta things.
I would Totally be Alice shes so awesome and I would love to see the future lol!!!