We have been to Tortola and loved it, but we loved it because it was laid back, no fantastic night life, and the water was the most beautiful I have ever seen. We went there specifically because it is the closest thing to the old, undelveloped islands of many years back. This is due to the harbor being too small for the large cruise ships to dock there.
We stayed at the Sugar Mill Hotel which was somewhat near Cane Garden Bay, but we never went down there. We made snorkeling trips out of Road Town, a couple of trips to Peter island, did some walking, ate mostly at the hotel, but some other places as well. If we had had a car we would have done more exploring. For what we paid for taxis we could have rented a car.
The best beaches are at Cane Garden Bay and Long Bay Beach Resort, but I don't know about pools. If there are bikini wearers, they would be at one of those places.
We have never been to Key West so I cannot make any comparisons.
We have been to a lot of different islands in the Caribbean, but not to stay--just for a day's visit off a ship.