American medical wages are above the world average, but medicine is one of the highest paid professions throughout the developed world, including in Canada (and yes, moreso than pharma PhD researchers on average, especially if one pursues a more lucrative specialty). Probably this should not be the determining factor.

The outside view would be that probably American medical wages will not plummet in the next 6-8 years, although that's a fairly irrelevant question (a career extends for decades).

or goes to a medical school in the Caribbean (where getting into them is apparently easier than mainland medical schools, but to complete the training takes six years)

These schools tend not to do as well in placements for residencies.