Hi, Ive lived in both cities, and rotated at Pitt.
Both are excellent surgery programs, people in the surgery program at Pitt are friendlier - it is a hard working nonmalignant program. Both are well funded for research and surgery facilities.
Pitt is less expensive, clean, like a small version of Chicago - complete with a dozen suspension bridges and a skyline. The economy is kindof blue-collar and not industrial like before. It seems to have diversified since the rust belt days of the 70s and 80s. Some pharmaceuticals and other clean industries.The trees there are huge, sometimes the sky is grey and it rains. Thats about half the days in winter that its grey, and every third that it rains a little. Its no Seattle. You can buy a huge house there for cheap. (5 min from campus, 4 bedroom, 3 bath, 4 stories for $170k) Theres several cool entertainment districts, fueled by 7 universities, including Carnegie Mellon (super famous for engineering, science, and robotics) UPitt (huge student population) and multiple other private colleges - I couldnt keep count. Nice law school, a business school. Great residencies all around, but many residents there say that their top 10 surgery program is their flagship - it makes the rest of the programs look even better. Theyre nice, in the OR and out. They get whatever fellowships they want, and even the alums love their school and keep in touch with their former faculty and chairs (no hard feelings, thats a good sign.)
Ann Arbor is grey 4/5 of days or more in the winter, it doesnt rain there as much as Pittsburgh. Its a long, bone chilling, burning cold winter every time. Its dirtier. It is more expensive, tough to buy a house alone. There is one large college there, lots of people to date, great college sports but no pro sports teams. Great live music scene, especially Jazz. Every program at UM is tops, which may be why they have some attitude, like a pseudo-Ivy. The surgery program is acknowledged by all as among the top few in the list of top 10.