I would strongly recommend that you do not look strictly at volume of surgical cases, but ask residents at the programs to which you apply if they have a good miz of supervision.
I trained at Colorado at it went something like this
R-2 year - 4 months University - little operating and mostly not as primary
4 months Children's - tons of operating mostly as primary
4 months County - tons of operating about 50% as primary
R-3 year - 4 months VA - tons of operating, primary depends on how good your chief is
4 months University - moderate operating mostly as assistant
4 months Private Hospital/Research - plastics essentially, little as primary
R-4 year - 4 months University - good operating significant numbers as primary
4 months Kaiser - tons and tons of operating vast majority as primary
4 months Children's - chief, operate as much as you want as primary
R-5 year - 4 months University - chief, operate a ton, all as primary
4 months VA - chief, operate as much as you want as primary, but you'll be taking cases away from your jr resident
4 months County - chief, operate a lot, all as primary
I finished with over 3,000 cases in ENT. Granted most were at children's. I think I did 432 as primary in my first rotation their as an R-2 (it's not unusual to do 15-20 cases a day their that rotation but it's all tubes and tonsils to start)
I had a great mix of supervision and autonomy. I don't think I would have liked it on one extreme or another. The university rotation was the best because you graduate in autonomy each year and it was not uncommon to be left alone on major head and neck cases in your chief year for the extirpation parts anyway. Same went for ear cases and others.
Don't look for volume alone, I've heard of a major program in CA where you are primary from the get go and do a huge volume no matter where you rotate, but I've heard a lot of complaints that people wanted to have more opportunity to learn surgical technique, not just getting through cases.
that's really all I have to say about that.