Haven't chartered in either location but have sailed my own boat around both. I prefer Guadeloupe as you have Isles des Saintes and Marie Galante islands as well as mainland destinations such as Deshaies. Also, if you have more time and feeling a bit more adventurous, wonderful Montserrat and Dominica. As for charter companies, I used Dreamyacht out of St Martin earlier this year and was very impressed by the quality of the boats and of Dreamyacht's service and facilities. I wouldn't hesitate to use them again. Other options... Sunsail operate out of Martinique but not Guadeloupe. Don't think Moorings do either.