I go to a T-25 and when we have visiting professors here they are terrible compared to the quality of education you get from the actual profs. The subject matter may be the same, but that doesn't mean you learn it as well. That's one difference.
I had a visiting professor from Yale that was absolute bunnies, so that's just plain anecdotal evidence that at the very best is worthless.
Not to mention, law is not complicated, you should be perfectly capable of learning what consideration is even if your professor is a homeless guy spending half the class masturbating at his desk.
I disagree that it's anecdotal evidence. An anecdote is one story intended to evidence an entire pattern of activity. What I have just described is the entire pattern of activity. Every visiting I have had was terrible and all but one permanent prof. I have had was amazing.
Saying that the law is not complicated is sort of ignorant too. Obviously, I can (and did) figure out what consideration is on my own. However, I have a limited amount of time within which to do my studying and attempting to figure out what most of the securities act means without the guidance of a competent teacher stretches the boundaries of the amount of time I have.
I do think, however, that your experience with a visiting at Yale demonstrates a key difference between the T-14 and lower ranked schools. Profs. from my school probably visit at yours. My school gets visiting profs from T-3s.