Often really bad "sites"will have some good rotations on them. Good "sites" will have bad rotations at them. In the end its all equalizes out. It also matters what you define as "bad". Some places will not supervise you very much and its up to you to see your patients, write some notes, and learn about the diseases and treatments and why the team is doing what they are doing. Other places will "hold your hand" and have lots and lots of didactics. Depending on how you learn either one could be amazing or a diseaster.
I was at one of my schools worst sites.,but at the end of the year I can look back and say that I learned a lot, and there were still some good rotations.
What determines the crappiness of a rotation has almost nothing to do with what kind of medicine it is, it has everything to do with who you are working with.
Example: Surgery at a huge level one trauma center lots of patients etc........may sound awesome, but if there is a lot of turnover of residents,interns, and students, then the attendings will not get to know anyone really well. If they dont know you, they dont trust you, and wont ask you to do things like suture and assist. It doesn't matter if its a crazy procedure that rarely happens if your standing in the corner.
A smaller hospital may give you a better surgical experience if you are working with a single attending, because then they get to know you and understand your skill level.