I remember somewhere along my training talking to one of the NICU attendings, who would take in house call. He mentioned the only consulting physicians he would see come in overnight were the pediatric surgeons and the pediatric cardiologists.
Obviously anecdoctal but pediatric cardiology as a field is rather rigorous, not just fellowship but also as an attending. A comparison is hard because residencies themselves are so different (same with fellowships), so comparing the two against each other gets to be even harder.
Some programs are more malignant than others. The factors are whether the program does in house or home call, number of fellows, volume, and whether patient care is fellowship dependent or not. What I mean by the latter is that some programs would keep running if the fellows didn't exist, so that the fellows are there to learn (and attendings don't get bent out of shape if a fellow is not on service for a period of time). Other programs need the fellows to work to manage the volume in other to keep things moving smoothly.
In retrospect I think my residency and fellowship programs were pretty laid back, which suited my style. Comparing the two, I took less call as a fellow and it was home call, but the actual work days were longer and busier. 4th year fellowship is a different animal. I was on call every day except for vacations and often flirted with 80 hours per week.
