Stony Brook is definitely isolated, but that shouldn't stop you from going out if you wanted to. I mean, there is a train station to Manhattan literally next to the campus (~1 hour ride).
If your calculations are correct, and if I had to choose among 3, I'd go with the cheapest. At the end of the day, if they are similar, making you a proficient dentist out of school, hey, I'd live a bit further away from family for thousands of dollars difference. Maryland is still... not... that... far... either. Then again, I would drive to schools, so it might be different if you are not. It's also in a city if you prefer a city lifestyle.