“Since most kids in that school came from all over the country instead of in-state like Michigan or Georgia Tech, you probably won’t feel as much like an outsider and will find it easier to make friends.”
Caltech is tiny compared to the other two schools. Michigan has a large OOS/International community. There are excellent reasons for the OP to attend Caltech, but lack of internationals will not be one of them. Now if the OP is male and is interested in the opposite sex, then Michigan wins that debate hands down.