I would choose Dartmouth. You get the best of both Cornell and Williams, a small community with focus on quality undergrad education while at a strong research institution. Also Dartmouth is definitely less cutthroat than Cornell and the quality of life is better there for most students. Also Dartmouth is slightly more prestigious than Cornell for undergrad if u care about this kind of thing. So unless you are going to be a hardcore engineer in which case Cornell would make sense then go to Dartmouth. Even if u wanna study engineering but you want to go into business or med schools Dartmouth is a much better choice. Not as much grade deflation as Cornell, not as cutthroat, fewer people --less competition and also Dartmouth is more of a target for business recruiting than Cornell ( although Cornell does very well too).