I'm not familiar with Brown, but I interviewed at Pitt and Northwestern. This is what I saw:
Pittmed:
-WISER sim center was awesome
-Curriculum was streamlined yet jam packed. It was very well-thought-out and every minute of the day was there for a purpose. But there was not much down-time. They are also innovative w curriculum and tweaking things in response to student feedback
-Clinical training was strong due to extensive UPMC hospital network, lots of patient diversity
-Research is strong, and scholarly project is required. Pittmed is trying hard to break into the top ten ranking and has been rapidly rising in ranking the last few years, I picked up on an "up-and-coming" type of vibe which I liked
-Location is surprisingly beautiful, more small city feel than Chicago, more natural beauty with all the rivers, trees & hills
Northwestern:
-Great downtown location right next to lake
-Most students live right near the school
-Curriculum is way streamlined (4 hrs lecture per day) w lots of free time for studying/partying.
-possible to do a concurrent MPH w/out adding an extra yr
-Nice academic facilities and hospital, some patient diversity, but not as much as Pitt
-Lots of younger 7yr bacc/md students from NW undergrad
-Students overall seem happier and more friendly at NW, not that they weren't happy at Pitt, Pitt students were just seemed more serious and busy overall
Between Pitt and NW, I would say choose Pitt if you want the absolute best academic and clinical training and don't mind the extra work, and like the smaller city atmosphere. I would say choose NW if you want excellent training but still want time to relax and have fun w other students, and would enjoy a big city downtown experience. I think both schools would give you the same types of options residency wise. I would personally choose Pitt but that is based on my situation and preferences. I would be very happy at NW as well, and if I were a young single premed I would go there over Pitt.
Feel free to PM me if you want to compare our interview experiences further. Congratulations on some great choices, good luck with your decision!