CGB said:
I've ventured out with both of these - enjoyed both
There are others - but since I don't remember going out with them, I won't identify

In order of fav:

www.bluewaterdiversbvi.com (Sopers & Nanny Cay)
www.sailcaribbeandivers.com (East End)

Unless you can gather a group of size - you go where they decide to go that day
So - phone calls the "morning of" might be the deciding factor - plus - which end of Tortola you are sitting on.