It depends on the med school, like med students at johns hopkins are really stressed out, but in general the stress levels in med school are really low, and they have tons of free time..
Part of it is that once you get into med school you're set career-wise.. you WILL graduate, you WILL get an internship and residency, and then you WILL get a job for 100k-600k (depending on specialty) which, barring extreme incompetence, you will never be fired from
In law school, it's easy to fail out, and depending on your school, you will probably have to get very good grades to ensure good career prospects
It's true though, law school does get easier after the first year
One of the posters here is married to a med student at vanderbilt, she can probably say more about this