No, not everything is about that, but a significant part is, especially with all other things being equal. Even if they weren't equal, one would be hard pressed to find a top graduate of a Carribean school matching up with a residency, over even a bottom-of-the-pack Harvard student. I would imagine that one need not go as far as the Carribean, even, to make that point - it may even be true for a resident of "Southwest State University" vs. Harvard, as far as academic reputation.
It's kind of like the winner of the N.I.T. basketball tournament (of those teams that don't make the NCAA tournament) being known as the "66th best team in the country." And in truth, they aren't even that.
When I was working in a hospital, a physician friend/mentor of mine told me that if I was serious about going to medical school, that I should apply broadly including the Carribean. That same doctor later rescinded that opinion and gave me an article that questioned the quality of education at a Carribean medical school, citing that the curriculum is geared towards passing the USMLE rather than preparing one for the practice of medicine.
Of course, everyone has heard a story that will back up either side of the argument, as evidenced earlier in this thread. But I would tend to agree with the poster who stated that Carribean medical schools are by their very nature a "second choice." And in truth, probably more like a "distant third" choice, behind osteopathic schools, especially as far as residency matches are concerned.
Just my two cents.