Stonybrook and Buffalo are probably pretty comparable in terms of price, education, and clinical experience. They differ in other qualities such as class size (Stonybrook <40, Buffalo 85), location (economically depressed part of the state vs way out on the island), winters (bad in Buffalo vs less bad at Stonybrook), and size of apartment you can get for your money (more apartment for your money at Buffalo). I think your class may be a little more diverse at Buffalo since the size is so much bigger.
UNC has lots of sports pride whereas Buffalo and Stonybrook have zero sports worth cheering for and zero school spirit. I have heard Chapel Hill is a fun college town to live in; Buffalo and Stonybrook resemble nothing like college towns. UNC also has one of the best ortho departments in the country, but that doesn't mean much for a dental student. Other than that, a decision for UNC vs the NY state schools probably comes down to cost and location.