Life-Changing College Question - Advice and Opinions Needed?

First of all, congratulations. You're obviously very talented to be able to make a choice like that at all, and you should be proud. That said, I think you're making a mistake if you decide on selectivity alone. Forget the alumni for a minute: what are the current professors like, and what kind of work are current students putting out? I'm sure you'll find a way to get along at either place, but you may have a rougher time of it if USC really doesn't gel with your style.