I'm surprised your friends said there's nothing to do at Stony Brook. Stony Brook has tons to do in the area. First, you're a train ride away from NYC, Northport, Huntington, Port Jefferson, etc. There are shops, museums, beaches, malls, tons and tons to do. The campus is huge with lots of groups and activities and people from around the world. There are activities and festivals and all kinds of things going on year round within an hour of the campus.
Oneonta is in the middle of nowhere - Stony Brook is in the middle of Long Island - huge difference. There's tons to do at Stony Brook and on Long Island and in NYC.