Esc, there appears to be a difference favoring GEMS but comparison isnt necessarily fair because DPMS has only been around since 2003 and GEMS since 1977. Both are great programs b/c you end up in an excellent allopathic school if you do well. However, DPMS has a higher failure rate (about 40% dont make it to DUCOM) due to the MCAT requirement to complete the program and overall the students seemed less family-like than GEMS. Also, I kinda got the vibe that DPMSers are not seen as equals in the school, but this is only MY impression and, really, who gives a crap, you're in med school! The best part for me about DPMS is that you'll end up in one of the most technologically advanced med schools in the nation (beautiful, new facilities) with a reputation that is quickly rising (their match list is ivy league-esque). As for GEMS, I dont need to explain, you saw it for yourself - just AMAZING.
If I was blessed with a chance to attend both, I would choose GEMS for the added prestige and the family atmosphere but I would be equally psyched to be in DPMS.