For all practical purposes, there is really no difference in the end which school you obtain your degree from. But, to directly answer your question, both schools train and prepare students equally well for residency, and program directors who are "open-minded" and are actually willing to consider applicants from Carib programs know this and interview candidates from both. St. George's is also in the same boat.
I will tell you, as a resident in a University-based GME program that is about 70% U.S. allo grads, 20% DO, and the rest U.S. or foreign IMG, it makes absolutely no difference where you went to undergrad med once you get into a program. No one cares anymore, and you will be judged solely on your work ethic, how you get along with your colleagues and patients, and whether or not you are a competent clinician. If you can succeed in all three areas, you will sail. And, just so you know, I can count on no hands the number of times I've been asked by a patient where I went to medical school. Get it?
So, pick a school that has a track record of placing graduates in the type of residency you want in the city/location/program you want. Do well on the boards. Get good LORs. The rest will fall into place.
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Ross '05 Graduate
PGY-1 Prelim Medicine
PGY-2 Anesthesiology (July '06)