If you know how to anchor, then I would recommend using your ground tackle rather than a mooring ball in the BVI if you have a choice. Many of the anchorages now have so many mooring balls that finding a spot to anchor outside of the mooring ball field is quite difficult (I anchor in 50-60 feet of water in The Bight on Norman Island, deeper than most charer boats have sufficient chain for).
The reason is that the mooring balls are not always well maintained by Moor-Seacure and because so many charter boats will run over the pennants and mooring lines and fray the lines. Many boats have broken their moorings in light weather and benign conditions. Below is a picture of a mooring that I took after I watched an (empty) charter catamaran break free of its mooring in about 5 knots of wind and managed to get aboard and get it moving before it hit any other boats. With the help of some other boaters we moored it elsewhere and the charterers who returned after dark had a bit of trouble finding their cat!
Companies such as Moorings now require that at least one person capable of driving the boat remain aboard at NPT Moorings such as at the Baths on Virgin Gorda, where Moorings lost a boat a year or two back due to a broken mooring.
Some anchorage in the BVI have bad holding and a mooring ball is a great thing - Great Harbour on Jost van Dyke to name one.
The waters are so clear and warm in the BVI that diving on the visible portions of a mooring system make a pleasure out of a necessity.