It should be noted that most of Dartmouth’s graduate programs are in the sciences. In other disciplines, Dartmouth’s size may work to its advantage, even accounting for the differences in undergraduate enrollment. For example, Dartmouth has twice as many professors in disciplines like classics, history, sociology, and anthropology and a fair bit more in other programs like geography, philosophy, and political science. With more professors, you get a greater and more diverse array of courses. Glancing through some department websites, Midd seems to rely noticeably more heavily on visiting professors than Dartmouth does.
Whatever the flaws of the USNWR undergraduate teaching survey, it’s noteworthy that Dartmouth is one of the very few schools to consistently make the list. Dartmouth is relatively unique among its peer universities and is not just yet another college of its type.