I've done several charters out of St. Martin - including Anguilla and St. Barts. I think the winds/weather is comparable to the BVIs.
There are far fewer anchorages - mainly because there are fewer islands. There are also far fewer readily accessible beach bars and restaurants as well as places to get water and provisions.
Chartering is very much a niche segment compared to BVIs. It's focused primarily on land tourists and super yachts in my experience.
Happy to answer questions about SXM if interested.
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