GT is much more intense because your grades are based on the med school student's curves! and obviously med students are studying like hell.
designed more for those that need a GPA boost and already have decent mcat, and want to go to a low-tier private school.
BU has 2 med school classes only (i think), and the rest upper-division type courses. It allows GPA boosting, rec letters, volunteer clinical, research, etc.
same year application is discourages.
In my own judgement if your GPAs ok, but not highly competitive 3.5+, and you don't have any publications, unique experiences, or such things preventing you from getting in, this programs better for you.
Anyway, I'm not certain of any of this, but wanted to put it out, so my misperceptions can raise better understanding/questions