hey Scotches,
I was accepted to both UB and SB, and I will be attending SB this year. In terms of reputation ( I'm sure i'll get yelled at by somebody, remember its only an opinion), SB has the best, but UB is also highly reputable. Both have excellent research opportunities, and both will train you to be an excellent physician. I think you should go to the one that you feel most comfortable with, and will be happiest at, and not worry about the reputations too much.
If you're a winter person, and love (and i mean LOVE) snow, then buffalo or upstate might be good for you. but if you want half-decent weather, then spending four years on long island isn't so bad. SB is an hour and a half from NYC by train, which isn't so bad, but SB is way out east on long island, and its definitely not an urban environment.
All three schools you mentioned have associated undergraduate institutions, so there will be that 'college' atmosphere at all three, if that's what you want. The area surrounding SB is beautiful, you can live in some really nice areas. But then again, the cost of living at Buffalo is much less than SB. I don't think you can go wrong with either (and i'm only speaking of UB and SB because those are the ones i got into, not because i have anything against upstate). also keep in mind where you want to do residency, b/c if i remember a good portion of UB people stay in the UB area.
--just my 2 cents
