We have used Sail Caribbean and Dive BVI. Both were good.

Met SC at Trellis and dove at the Dogs - Chimney & Coral Gardens.
Met DBVI in the North South and dove the Rhone - Bow & Stern.

The dive site options will be limited by where you are being picked up from, weather, and conditions. Favorite dive sites for us are - Rhone, Wreck Alley, Marco's Point, and Angelfish Reef. Coral Gardens is the best on the north side and includes a small plane wreck to check out. The plane has a cool story too