It depends upon your medical school, some are a lot more "cush" than others in years 3 and 4. I would say residency in a given field is actually less variable than medical school.
Some places will pass you on your rotations if you merely show up everyday, with no expectations beyond passing the clerkship exam.
Some places give their medical students 3-5 days to take off every month any time they want.
Some places have no call expectations for medical students.
Then there's schools like mine which make you come in on national holidays, which assign you two extra nights of call for taking a genuine sick day, which tell you the 30 hour rule doesn't really apply to med students on call so they can keep you as long as they want post call, which give the residents and attendings 100% subjective power to decide your grade on rotations, which assign call the night before exams, etc.
Coming from my school, I think all the graduates have found residency even in the most unpleasant fields to be easier.