For most students, the purpose of getting an M.D. is to practice medicine. Because the United States has a number of licensing requirements and exams medical students must pass in order to practice medicine, it is important for a prospective medical student to consider where he wants to practice. For example, the United States uses the United States Medical Licensing Examination (USMLE) for licensing, whereas Europe uses the Professional and Linguistic Assessments Board (PLAB) examination. Schools in the United States teach to the USMLE, whereas European schools teach toward the PLAB. Consequently, a doctor's licensing exam scores will be better if he attends medical school in the region he wants to become licensed to practice medicine.
If you plan on practicing medicine in the United States, you need be sure that the medical school you attend is recognized as the equivalent of an accredited program in the U.S. Some states, such as California, review foreign medical schools on a case by case basis rather than accepting a region accreditation. For example, while medical schools in the Caribbean teach toward the USMLE, very few of them are accepted as accredited-level schools in the states that review individual foreign schools.
One benefit of attending a foreign medical school over one in the United States is that the cost will likely be significantly less. Doctors graduate with a mountain of debt from student loans, especially if they went to their undergraduate program on student loans as well. For some students, the prospect of going to a school that is good enough to secure them positions as practicing physicians in the United States, while graduating with less debt, is an attractive option.
Most medical students want to get the best education they can, so they can become the best doctors they can be. An accredited school in the United States is a mark of the quality education a student who matriculates there will receive. With foreign schools, there is no similar brand that guarantees the quality of instruction. Students can get a feel for the quality of instruction at a foreign medical school by looking at how its students do on the USMLE.