We have a cat with TMM and we couldn't be more pleased. This is our second. The first, a sloop, was with Sunsail and then BVI Yacht Charters. So, we have a pretty good understanding of the market.
While there are advantages to St Thomas, we have picked the BVI twice simply because that is where the majority of charters go. It's worked so far.
Why TMM? They gave us the best price on the boat and we know how well they maintain their boats, based on ten plus years of sailing with them.
Go for it.