i only have a few things to add that may be worth thinking about:
while the yale system is truly appealing, the maximal benefits seem limited to the first two years - with 5-6 more years of a program to go. though cornell doesn't offer the quite the same degree of a laissez-fair approach to medical school, it is an extremely flexible curriculum that allows for students to choose structured rigor or forgoe it (many of us are in the latter group, and being as this is board study time for us, none of us are regretting our 2 year long stance). i would also offer that the diversity of clinical training in nyc with the large network of NY-Presbyterian hospitals is nearly unrivaled (and contrary to popular belief, private/no insurance patients do not make up even a large minority of NYH's patient base, with medicare/medicaid making up a sizable fraction).
with regards to research, unless you have a specific person in mind at either institution, the breath and depth of cornell/sloan kettering/rockefeller is hard to beat. and since the latter two institutions recently began large faculty recruitment drives and physical expansions, the offerings will only increase over the next few years.
finally, don't underestimate location. i'm not in the school of thought that considers new haven an abyss, but i think that nyc and the tri-institutions offer opportunities that one often doesn't even think of on the outset. i thought i'd be missing out on a college campus by coming here - and i'm now quite certain that i'd have missed out had i not come here. if you're not a city person, however, that's another issue. and if you simply like yale, and don't like cornell - far be it from my to convince you otherwise. best of luck with your decision and wherever you decide to go.