Reputation wise, Northwestern is probably a little better, although that's not saying U of C is not good. I think most of the programs in Chicago are all great. One program to check out too is Rush. They have some big name attendings, and are more involved with research than Northwestern. I rotated at Northwestern, so I'll give some info about it, don't have any experience with U of C.
Northwestern is a pretty cush program, with 9 residents each year, and although NMH is a Level 1 trauma center, there really isn't all that much trauma. Strengths of the program are sports, peds, and maybe joints. Several of the attendings take care of the Bears, Cubs, and Blackhawks. Weaknesses, would probably be trauma, although the residents do rotate through Cook County for 3 months as PGY4s. The residents admit that it is a weakness, but then when as a community orthopod, are you really gonna do a complex acetabular fracture on your own anyways? They do have a fellowship trained trauma guy, but the volume is just a little low. The residents are comfortable taking care of any type of long bone fractures that you would see in the community though.
Operative experience is variable. At NMH on some services like joint or spine, you're going to be holding hook as a PGY2 or 3. You start to do the cases as a senior. On the sports service, you do about 50% of the case, even as a senior, and pretty much just watch when they have the professional atheletes in there. In Evanston, the residents do get to do full cases as juniors. The VA is pretty much total freedom. One thing to realize is that the type of experience is different at Northwestern. As a resident you may not be doing a bunch of trauma cases with a lot of autonomy, but you will be doing a bunch of elective cases. In terms of something like sports, some of the residents feel like they might not even need a fellowship because sports is so strong here, but do it just to improve their chances on the job market. All the residents do go into fellowships, with the majority going into private practice.
The didactics at Northwestern are really strong too. There's conferences every day, including Saturdays. The residents all read a ton, especially for fracture conference because it's run by residents and they don't want to look retarded in front of their peers and for Chairman's conference on Saturday. During the summers, all the residents do anatomy, with the PGY3s dissecting, and the PGY5s and attendings teaching. So you get anatomy every year that you're a resident, which I think is a great aspect of the program. I rotated here, and at 2 other programs, and I think knowledge wise, Northwestern residents are probably the smartest. But operative wise, may be a little lacking in experience.
Overall, I think Northwestern is a great program, and it's definitely at the top of my list. If you really want to go there though, you should definitely rotate, since Northwestern heavily favors their rotators.
I'd be happy to try and answer any other questions about the program.