So I'm biased since I chose a large Ivy over a large public college back when I was making this decision. That being said, I think the biggest difference is just your access to potential advisors, mentors, etcetera. While I don't know what it would have been like to attend places like Texas A&M and other schools on my college list, I think the access to research, funding awards, and extra-curriculars I experienced was fantastic. However, as someone above me mentioned, you really make your own experience. Aside from the mandatory freshman advising sessions and declaring one's major, at my undergrad we weren't required to meet with professors outside of class for advise or anything else. So, you have to have the initiative to know what you want out of the college experience and go for it, regardless of whether or not you attend say the University of North Carolina or Columbia, Penn, etcetera. Finally, I also think that the experience of being a gunnerific premed may be different at Ivy type schools at least in separating out the A's and the B's in a given science course. Competition can be beyond fierce.