I've been both a non-tenure-track (NTT); I am now on a tenure-track (TT) professor; and I will soon be a tenured professor. I've been in the position of evaluating non-tenure-track instructors. (First off, a correct on the terms of art: very seldom is a NTT faculty member titled "professor.") In my experience, yes, NTT faculty are much better teachers. From working as an NTT faculty member, working with NTT faculty, and having them as close friends, I can say that there are three reasons that NTT faculty are better teachers. 1) They are younger and consequently fresher and have fewer family obligations. They are typically single. When coupled, they don't yet have or don't plan to have kids. 2) They are under constant threat of losing their jobs, so they work very, very hard--much harder than should be expected of people working for, often, about $35k/year, sometimes more, but generally not over $40k/yr. 3) NTT faculty are teachers only. They are not distracted by research obligations nor by substantial obligations to develop/run the program. ALL THAT SAID, I don't think hiring lots of NTT faculty is a good thing, at least as it is done now. Such faculty are treated as disposable, paid just enough to keep them around a few years, and worked hard enough that they will burn out pretty soon anyway. That may be good for the students (as long as that student is planning on pursuing graduate work that will lead to one of these dead-end jobs), but it's not ethical. Granted, to some, those salaries I listed sound pretty good, but keep in mind that level of pay is not enough to support a family and it is often further reduced by the need to repay the costs of graduate education. The answer may well be to admit fewer graduate students, produce fewer doctorates. But, a lot of the quality I saw in the instruction of NTT faculty was the result of very strong educations; many of those faculty were electing to pursue significant and demanding research projects on their own dime/time. So the undergraduates (and the employing institutions) are often effectively getting the benefits of a young professor without actually paying for a young professor. That may sound good, until you're the person in a similar situation.