Well, here are my thoughts on the pre-clinical training. I do have thoughts about clinical training, but I'll let people with more experience (i.e. med students if possible) comment on it because I am sure I'll leave some stuff out...or just be oblivious to it in general!
I would say that the quality of the pre-clinical training is influenced by a few factors. First of all, there is the quality of the instructors and whether or not they are engaged, interested and accessible. Second is the quality of the academic environment. By that I mean the extras such as computer based training, facilities, revamped curriculum (up-to-date and not unnecessarily redundant). Third, for the pre-clinical, you can take into account the student body and whether or not they are competitive and if they grading system fosters cooperation or competitiveness.
Hope that helps...and that someone who feels more confident on the clinical years will respond to this thread.