I too grew up in Chicago (best city in the world- we were ROBBED of the Olympics), and got into both NW and Pitt, but am now at Pitt. It was a tough decision, yes, but it ultimately came down to the following factors (in order of importance):
1) Pitt has better clinical resources, for all the reasons enumerated above and more- NW is kind of contained in N Chicago, which is a nice area to walk around, but you won't get the entire patient diversity that is Chicago because there are four other medical schools, and you can forget seeing many suburban/rural patients (unlike Pitt, which has all of W Pennsylvania as well as E Ohio, all of WV, etc.)
2) Pitt has a lot more research money, basic and clinical, so there is more and better research in general going on, and more funding/opportunities for me to do research, get published, get good letters for residency, etc.
3) Yes, Chicago is an awesome city (it's my city, after all
but as someone who has many friends and classmates now downtown, it's an expensive city to live in, like NYC and LA. As a med student, you are basically below the poverty line. Cities like Chi-town, NYC, and LA are all great- if you have a lot of money. You will not. I would rather do residency in Chicago, or be in my late twenties making bank and enjoying the town then. Your financial aid for housing/expenses goes farther in Pitt, plus it's no cowtown anymore... there's a hell of a lot to do here, even for a comic book geek/ethnic food gourmet/dance clubber like meselfs.
I cannot speak too much on Baylor, as I decided not to apply there- it's a great school, don't get me wrong, but having TMC is not an end-all, be-all, especially as Baylor does not own it, it's just affiliated with it. Read: you can't just walk in like you own the place. Unlike UPMC.
But in the end, they are all great schools, so you have to decide which means more to you- career or lifestyle.