Hey,
I was in the same dilemma as you were. I'll just tell you what factored into my decision and I hope it helps.
1. Money. I loved GW's location but the price was just outrageous, both tuition and rent and cost of living. Additionally, I'm pretty much not eligible for any grant-type aide so any school would have probably been cheaper than GW. Which brings me to MCW. It's "relatively" cheap for a private school, and the cost of living is pretty ridiculous, in a good way. I mean getting a big 2 BR for 750 TOTAL!!!! I'm paying that much for a studio! You're going to be paying twice what I'm paying for a studio in DC. I remember them telling me its 900 for a hotel room (essentially a studio) that doubles as their "med-student dorm". Though Milwaukee isn't going to be DC in both location and weather, its a decent city from what I've seen (I'm living in Chicago). Fair amount of light life, restaurants, random things to do, shopping and the like. Also I like how parking will not a problem for me. I'll have a car and that is definitely impossible/headache in DC. Not a problem in Milwaukee/Wauwatosa. Trust me, after living in a big city for the past 4 years, I'm sick of driving around for half an hour looking for a street spot, only to have to park an SUV into a tiny space that a smart car would have trouble with. PM if you want price comparisons.
2. Research. MCW, though not a research juggernaut, does a fairly big amount of research. Since I'm looking to specialize, I know research will be available for me to do. However, I'm assuming GW, with DC and NIH just around the corner, also does offer lots of research opps. However, just based on the match lists and "feel" of both schools, it seems like MCW is more research oriented and GW more primary care, although I'm guessing the distinction may not be great.
3. I loved both schools facilities, but MCW's was just really impressive. The brand new (well I guess couple year old) building was so nice. MCW's library, centrally located, was great. Bright, and somewhat happy, at least the building was. I could definitely envision myself burrowing myself there during exam times. GW's library seemed a bit like a bunker, which I didn't like. The hospital at GW was definitely impressive. I didn't really get a chance to look at MCWs, but from cursory look, it seemed like a serviceable teaching hospital.
4. Ranking/Reputation. Didn't factor really into my decision but MCW is in the top 1/3 in terms of ranking (last I checked 52 research, 46 primary care). GW is not. However, this is probably not a big deal, unless you want an ego boost. GW probably has a better "street/layman" reputation, being attached to an undergrad as well as being in DC/East Coast. MCW, though not as well known (someone asked me if it was DO or MD), has a very strong physician and academic reputation. MCW has a strong midwest reputation as well. Again, ranking and reputation wasn't really a factor for me, but maybe this paragraph will help.
5. It seems like MCW wants you, whereas other schools just seem to say, "Ok, come if you like." The only issue I have with MCW is diversity. As a minority myself, GW's diversity was definitely a plus. But its not like MCW has no diversity either.
That's all for me. What are you leaning towards? What factors are you thinking about?