Why does everyone assume that harder means better? Sure, one school might be harder because they expect you to know the material at a higher level and with less room for error. But a school can also be harder because it teaches poorly and provides few resources.
Imagine there are two schools, A and B. At school A, at the end of orientation, the students are taken to the library and told "In this library are books that have all the information you need to know for your preclinical years. Learn it. Also, due to budget cutbacks, there are no lightbulbs in here. After you take Step 1, we'll start you on rotations. Until then, get to reading." At school B, dedicated and skilled teachers present everything in a coherent way, provide both details and a big-picture view of how everything fits together, what's important, and why. They work closely with students over the preclinical years, teaching, testing, and helping students to identify where they're doing well and where they need more work.
School A in this example is undeniably harder, and undeniably much, much worse.