[mcguire]

The next two paragraphs go into more detail:

"One answer to this question would be following: One learns a lot more when taking calculus from someone who is doing research in mathematical analysis than from someone who has never published a word on the subject. [...] But this is not the answer; some teachers who have never done any research are much better at conveying the ideas of calculus than the most brilliant mathematicians.

"What matters most is the ambiance in which the course is taught; a gifted student will thrive in the company of other gifted students. An MIT undergraduate will be challenged by the level of proficiency that is expected of everyone at MIT, students and faculty. The expectation of high standards is unconsciously absorbed and adopted by the students, and they carry it with them for life."

I'm going to look funny at the claim of "expectation of high standards"; I suspect he's delusional.

But there is, in my experience, a considerable difference between "someone who is doing research" and "someone who has never published a word on the subject"; I've never met any "teachers who have never done any research [that] are much better at conveying the ideas." Further, the "ambiance" bit is right; being surrounded by people who are deeply interested in a topic beats the pants off people who are just there to get a grade.