I've done Moorings & Sunsail in Tortola.................both were fine.
I find Moorings more formal, less flexible (ie;more rigid with time schedule) & more expensive than Sunsail.
Both trip were summer trips.
Overall, Sunsail tends to offer more deals but are not as "fancy" as Moorings in Tortola (also different harbors) Sunsail is near the airport but away from Roadtown (main town / activity).
St. Thomas - often easier / cheaper to fly into from many cities in USA.
Tortola usually means changing planes in San Juan................or a ferry from St. Thomas (I've done both)
Sunsail has a website that will give rates & quotes ..............Moorings prefer to talk with You.
Pickup a cruising Guide - local marine book store, on line or directly from
will help plan your trip plus valuable travel info
Have not chartered from USVI but certainly another option to consider & sail to BVI is a good voyage considering many in BVI are so short. Jost Van Dyke is a very laid back immigration/customs stop (if coming in from USVI) vs Tortola