<p>The same may be said of the GRE's as well I suppose. I worked for many years in hospital settings and routinely saw the many hours residents were required to work, although some states have now put a limit on this it is still excessive. However, I have seen Ph.D. students and post-docs sleeping in their labs and tracking multiple experiments that required their attention for year after year. (We had a t-shirt that read, Grad school, not just a job, and indenture; we even had to ask permission to move or get married.) For example, a friend's daughter is spending a full year (not her first) living in a South American jungle under extraordinarily primitive and physically challenging conditions so she can observe and record a rare language, she is in her 8th year and has a couple left to go. She would love a cozy hospital to work in. I'm not sure one can conclude one track is much more difficult than another. A relative, currently doing a residency says he thought med school was easier than his high school, of course he said this about his college experience as well, perhaps one should avoid that high school.</p>