Beth, I've found myself choosing between the same four you have. I still believe that the three Derby entrants will probably take win, place, and show, but I'm not really a very good handicapper, so don't take anything I say to heart. ^_^
Having said that and seeing how Barbaro looks after his Derby, I'm going to hope it's him. Easily the classiest horse in the group. Brother Derek, I think, will give him the most trouble, but, also just an 'I think', he may be more tired than he seems. The other two, will probably battle it out for third and fourth.
So, my choices are:
1. Barbaro
2. Brother Derek
3. SweetNorthernSaint or Greeley's Legacy
4. Same as above.