Again, I think your talking more about specific professors rather than the course subjects themselves. Of course, I don't know which OP was actually referring to, but I'm talking about the difference between taking Engineering Economics and GenEd for Non-majors 101. Not the difference between taking Engineering Economics with Professor A vs. Engineering Economics with Professor B.

My first degree wasn't in STEM, so I didn't have any of those weed-out classes. Some people failed, but that's because they deserved to fail-- none of the professors made intentionally hard. I've taken a general chemistry course that some people thought was "hard," but it really was just that the professor was awful. It was actually easier, I think, then the "typical" chemistry course (it was a community college), but it just seemed harder because the professor was that bad.

Perhaps our difference is how we define "challenging." The content of my General Chemistry course was relatively easy (for Chemistry), the only thing making it hard was the (lack of) skills the professor had. In the scenario OP's referring to, I'm basing how "hard" a course is solely on it's content. Like you, I wouldn't take a "hard" professor just because he or she is hard. I would, however, take a "hard" class.