Its very difficult to rank these, and it does vary greatly by program. Here is my estimate best to worst lifestyle during residency:
1. Pathology (no intern year is key, daily schedule predictable, minimal stress)
2. Derm (basically no real call, minimal stress)
3. Radiology (call is relatively infrequent, but horribly busy and stressful when there. Some programs have very frequent call. Daily schedule very predictable and controlled)
4. Anesthesia (call infrequent, but have to get in at 6:30 am daily and the end of the day may vary more)
5. Optho (daily schedules less predictable, call not too bad, but may have to come in often depending on the rotation, some rotations very intensive hours, more stressful patient care)