<p>I would point out a key issue in determining 'what is hard/difficult'. I think we have to careful how we are defining 'hard/difficult'. My definition of a place that is 'difficult' is a place where it is more difficult to get top grades. Hence, difficulty is intimately intertwined with grade curves and grading philosophy.</p>
<p>Let me give you an example. Take premed, at any school - MIT, Stanford, Harvard, wherever. I think we can all agree that it is 'hard' anywhere. But why? Honestly, the premed material really isn't all that difficult to understand. It's certainly more comprehendable than most advanced math coursework. </p>
<p>What makes premed 'hard' is not the material, but rather the grading as well as the competition in the class. You can study extremely hard, understand the material very well, and still wind up with a very bad grade. Why? Because everybody else in those premed courses is also studying extremely hard and also know the material well, and the grades are harshly curved. To get an 'A', it's not good enough to just understand the material, you have to understand it better than most other people in the class, and that's no walk in the park. </p>
<p>Contrast that with a situation where the material is extremely incomprehensible to you. But if it is also extremely incomprehensible to eveybody else, and the class grade curve is not harsh, then you'll do fine. Case in point - I knew one guy who scored a 30% on one of his engineering exams. Did he cry? Not at all - in fact, he celebrated. Why? Because the average score was a 25%. And according to the grade curve, his 30% was good enough for an 'A-'. He had no idea what was happening on the exam. But neither did anybody else, so when it came time to curving the grades, it was a wash. </p>
<p>The point is, it's not enough just to talk about the comprehensibility of the maerial of various courses and whatnot. You also have to talk about how those courses are graded, whether there's a curve, how harsh the curve is, and so forth.</p>