As a current 4th year student at Duke, I can comment briefly on this. There have been a number of great posts on this topic in the past few years too, so I encourage you to do some further searching. But basically, in my experience at Duke and having talked to a number of friends at other schools, we don't work any harder than anyone else. It's really a misconception that we somehow "cram" two years into one, for a number of reasons that were discussed in prior posts. Our first year is longer, and we simply don't cover certain topics that can simply be learned later on in medical school. Our first year covers what's needed for step 1, and we tend to score very well (reportedly #2 in the country in average step 1 scores). Many curricula cover topics like orthopedics, dermatology, and radiology during the 2nd year, and we simply don't cover them didactically. Students pick up such details through elective coursework during the 4th year, and through independent study. We simply feel that time is better spent on the wards, and I've definitely valued this approach, as more of a hands-on learner. I don't feel like I've missed out on anything. To the contrary, I feel better prepared to start my internship after having been on the wards earlier, with more time to process what I've learned and put it all into context. Although we spend the 3rd year doing research, we're required to do a continuity clinic, so a lot of integrative learning occurs during the 3rd year.
I'm not sure what to make of that comment about UNC being "a league above Duke." Just look at how well we match and then compare it to UNC's list; it speaks for itself. Most residency programs LOVE Duke students, and if we didn't perform at a high level as residents then they wouldn't continue to choose Duke graduates above those from other programs.
In short, I really LOVE Duke, and would matriculate here again in a heartbeat. I can honestly say that I wouldn't change a thing about my experience. It's been great! And I'd be happy to answer any further questions anyone has about Duke.