As I said, what differentiation there is is due to the initiative of instructors. I agree that this is an indicator, but it's still a somewhat indirect indicator. Often courses are also a reflection of what's popular at the time, or what might win brownie points for a particular professor or department.
If you want to find out what's really brewing in people's heads, it's better to just look up papers and talk to particular professors.
> As I said, what differentiation there is is due to the initiative of instructors.
This is clearly true. I just don't see why it merits devaluing an assessment of the courses. Quality of instruction clearly matters, and that's why I put professors immediately after. But if certain courses play to one's intrinsic motivations, this can be considerably more important to one's learning.
A great instructor teaching a subject you care little for can only do so much. But the opportunity to work on things that genuinely excite you can override having a poor instructor.
If you want to find out what's really brewing in people's heads, it's better to just look up papers and talk to particular professors.