I grew up, went to college, and am an m4, in Chicago. My family is all here and thought this is certainly where i'd want to stay for residency until i started my clerkships 3rd year. Pediatrics in chicago feels very different from that in other cities, perhaps not other major cities like NY or LA though. A lot of it feels more like a business with many of the pediatric hospitals (in realities small floors in the larger hospital) are just in existence with administration not really caring about them and with no interest in expanding them.
But onto U of C in particular which is a free-standing children's hospital unlike most of the programs in chicago. U of C has a great new facility, the building that Comer Children's sits in is wonderful. U of C as a medical institution, however, is having it's fair share of recent issues- both administrative and training wise. I'm not saying you will be a bad pediatrician coming out of U of C but that there are plenty of other places that will train you better and give you more opportunities. U of C fellowships have been unstable and some of them have simply collapsed in the last few years. While U of C still has some recognition because of its name it's not necessary an elite children's hospital. The PD and the associate PD there are super nice though and the residents seem happy. While some of the other peds programs have carved out their own niche per the chicago peds culture, it's hard to really say if U of C has a niche of their own because even their chronic care facility, La Rabida, is actually now a part of Children's Memorial. If you are not from Chicago and aren't simply trying to stay Chicago I'm confident you've interviewed at better programs than this. I definitely don't think this is a program worth leaving home for.
Good luck with your decision! March 17th cannot come soon enough!