Personally, I'd take Horford. You don't have to worry about his body filling out, and he's already the most polished post player of the group. He's doesn't have the athletic upside, but he could turn into a Boozer level post player in my opinion. And what's more, is that he doesn't have as much downside. Even if he fails to develop anymore, his body, toughness, and overall understanding of the game could give him a PJ Brown type career for 8 to 10 years. With Wright, he really doesn't have the perimeter skills to have much value should he never develop the needed strength.
Given team needs and workouts, I could see Julian Wright moving up, and possibly Yi Jianlian if he turns into one of those mystery men who no one knows about his competition level, and he walks in to some gym and hits a bunch of threes after measuring 7-1.
Thornton from FSU is a stud of an athlete, but he's a bit of a tweener, in that he plays a little closer to a PF, but he's only 6-8. That type of player may be gaining more value these days though. His biggest problem may be that he'll be 24 years old by the middle of next season, so I'd be leary of taking him over some of the younger guys with more room to develop.
After "the two", you're looking a cluster of Brandan Wright, Al Horford, Corey Brewer, Joakim Noah (he is on the rise right now), Yi Jianlian (why?....I don't know), and two guys with an outside (and very slim) chance, Jeff Green and Julian Wright.
I think the 3 Florida kids and the Chinaman are probably duking it out for 4th after Wright. If someone was to knock Wright off, I would be Horford. I could see the right team going to Noah, but I wouldn't count on it at all. Still slightly possible, though.
It depends on the need of the team. I think Brandan Wright has the most potential, but some might need a big Elton Brand-type big like Horford or a shutdown wing defender like Brewer who can even guard centers if need be. It'll be one of the 3, my guess would be Wright though...