Another point I'd like to make re: diversity of patient population.
It certainly SOUNDS like Chicago would have a more diverse patient population (or NY, or whatever), but one thing you should consider is the "catchment area" (where those patients come from). NW is in a super ritzy part of town, and there are tons of teaching hospitals and great hospitals in general in the Chicago area. That means that regardless of the fact that it's a big city, the catchment area of the hospital will mostly be local because it's "competing" with other big medical centers in the city. This is the case in NYC, where if you're at Columbia you'll really mostly see just one kind of patient, if you're at Cornell you'll mostly see one kind of patient, etc...
Vandy has the "big fish in a small pond" thing going for it. We get everything under the sun cause we're it around here. Yeah, there's another academic center downtown (Meharry) but they actually mostly get "one kind of patient" as well because of the area in which they are. We have the busiest trauma 1 heliport in the country because we get emergencies from all over the south. We get patients from downtown, patients from the ritzy areas, patients from the very poor areas, and patients from rural middle of nowhere TN.
And yeah, I'd also think pretty hard about the PBL curriculum since that's really the main difference between the two schools as far as studying is concerned. Also, don't discount the gut feeling you got while you were there...that feeling is generally right.