Rockland is south of Belfast, and about half an hour closer to Rhode Island by car, even if you take I-95 to Augusta and Route 3 to Belfast. Rockland is also much more centrally located in Penobscot Bay than Belfast. Belfast is a perfectly nice harbor, but it is a bit out of the way tucked up there in the far northern reaches of Penobscot Bay. Rockland is a much better jumping off point, IMHO.