Living in the virgin islands, I know a bit.
STX- not touristy, great restaurants, some hiking, nice beaches, mediocre shopping
STT- the tourist @#&^hole of the Caribbean. Lots of shopping, poor beaches
STJ- very secluded, fantastic beaches, most beautiful of the USVI
BVI- range from touristy to secluded depending on which island youre on. jost van dyke is cool.
BVI requires a passport, USVI doesn't. STT has many flight with most carriers. To get to STJ you have to take a ferry from STT. STX has AA flights daily from Miami.