It's not the two years on the islands or bouncing around for rotations that would suck. It's the amount of debt you'll have with a high likelihood of not being able to get a position as a physician.
Here's a description and example of how the match works in general:
http://www.nrmp.org/match-process/match-algorithm/
then a specific example:
http://www.nrmp.org/wp-content/uploads/2014/05/Run-A-Match.pdf
But the bigger problem than the low match rate of FMG's is that Caribbean students have a hard time even getting to the point of applying to the match.
The schools are designed with a high attrition rate to make the school's numbers look good. The schools advertise a good boards pass rate and match rate, but the statistics are inflated because they screw with the denominator. A lot of students fail out before they take boards, others aren't allowed to take boards until the school thinks they can do well, and others aren't allowed to apply for the match if the school's don't think they can match. So yeah, of the people who are allowed take boards, the pass rate is decent. But of the students who start med school, that rate does suck. Of the people allowed to progress to the match, yeah, the numbers aren't great, but not abysmal. But out of the number of people who started carib. med school who actually match into residency programs, it is abysmal.
Of those who start in US MD programs, and I don't have numbers for DO schools but would imagine it's similar, less than 5% of medical students don't graduate. That's a big difference.