hey there, i went to mssm for med school and am now a resident at MGH. i loved sinai, and thought their IM program was top notch. there were great residents, and dr. babyatsky is clearly one of the best program directors in the country.
i would say IM at sinai is on par w/ columbia as the top residency in the city (though sinai has a better quality of life, whereas columbia is more hands on). and the clicnical training at both is much stronger than cornell, even though cornell has a great onc/cards/rheum focus. a little further down stream would be nyu and einstein, which also have great programs, but are much easier to match into.
sinai is also beginning to redo all their facilities and research programs, and it should be fun time to be on campus.
best of luck