I don't know man. I can buy a copy of a Flaming Lips album and know all the words and thoroughly enjoy the album but its another thing to hear then perform in person. Same with a lecture vs Wikipedia, especially if the prof is a gifted performer.
I think the "if" is smaller when you seek out that type of relationship. What I've found out, too late, is that most professors want to be that type if teacher and a good student can bring that out of them. You get what you put in. Wikipedia = a Wikipedia education. Seeking out a deeper interaction with your professor = a deeper education.
Depends on the professor. I have a business degree and some of my professors seemed to almost crave the ability to discuss beyond the topic. There's subjectivity in business too and where there is subjectivity, there can be great discussions to have. I would agree though that those moments are far more abundant in the arts.