I have not been to Saba so can't address that. I suppose St. Bart's is good for one visit, just so you can say you've been there. But since you love beaches, my vote is for Anguilla. Shoal Bay East has the most beautiful beach I've ever seen. It's a little bit of an expensive day, what with ferry fare, taxes, taxis, etc., although nothing like a day at St. Bart's would be. I think Anguilla is worth every penny and always want to go there at least once each time I visit SXM.

Let us know what you decide.