KenPom tends to overrate Virginia (and Wisconsin). I think it's because both those schools tend to have a lot of 70-40 type games against crap teams where they put up unbelievably good defensive numbers. They're both outliers that his system can only account for so much, and since the system is evaluating efficiency, it's always going to value a 70-40 win more than a 90-60 win (fewer possessions, so the 70-40 win was more efficient), when the practical difference is nil.
In this specific case, though, I'm not so sure that KenPom isn't a better gauge than the Vegas line. Virginia always starts out hot, and West Virginia hasn't looked all that great. I think the line is so high because of location, and because people are generally down on Virginia after they got slaughtered in the tourney last year. If I had to bet the game, I'd take Virginia.