for starters, Just do a simple search on letsrun threads for the 2 schools/programs. There will be no negatives on Vandy; however, UNC is flooded with negatives.
Nashville is a great place to live and train. Coach Keith is a great coach and cares about his runners as student athletes and people. They are true student athletes that enjoy running. Vandy is a great institution. They have a great freshman class this year and a standout sophmore so the future is bright. He recruits successful students that develop, IE he doesnt go to recruit in canada.
UNC is a good school but has been known to run his runners into the ground and many have rumored to have eating disorders (just look at team pictures and you will see why this isnt a far stretch). Watson isnt afraid to recruit canadians and violate recruiting rules.
In a short way to answer your question, Vandy over UNC in a heartbeat. Choose Vandy if you can get that type of education and running atmosphere. If success is important to you, just look at results.