The short answer is that there isn't a big difference between the two. Both are in Cleveland and associated with CWRU. They are of similar size. Both provide ample opportunity for procedural experience, and both have good track records of placing people into fellowships. The residents from both programs are friendly and seem happy (at least for OBGYN residents), and the call schedule for the two programs is similar.
As I see it, the differences are as follows:
1. Fellowships: The two programs actually share gynonc fellows. Additionally, Metro/CCF has MFM and urogyn fellows. UH has no other fellows, though they are applying for an REI fellowship.
2. Hospitals: At the UH program, all non-electives are set up at MacDonald house on the UH campus. For Metro/CCF, you go to Metro, the Cleveland Clinic, and Hillcrest hospitals. Hillcrest and Metro are 30-45 minuites apart, and CCF is pretty much in the middle of those two, but I wouldn't recommend living adjacent to CCF.
3. Electives: UH has a couple months of elective time available for things like international medicine, medical spanish, etc. Metro/CCF schedules all your rotations - there's no elective time.
4. Diversity of patient population: Both programs have diversity, but Metro/CCF probably has more. Metro is a county hospital located near what is really the only hispanic neighborhood in Cleveland. You'll also get plenty of white/black folk at Metro and a few asians/middle eastern. At CCF you'll probably see more rich, suburban folk than you will at Metro, and Hillcrest is located out in the 'burbs.
5. Bells and whistles: CCF is one of the most prestigious hospitals in the country and has all the newest stuff. Their surgical training facility was pretty impressive.
I think both programs are great - you really can't go wrong with either. As far as choosing, I think that depends on what you plan to do. If you'll be a generalist, I rate both programs equally. If you plan to pursue a surgical fellowship, I would rate Metro/CCF over UH. If you plan to pursue any other fellowships, I don't think it matters which you choose.