This question does not need too many explanations for those who are experienced sailors and undertake sailing vacations for years on their own or on chartered yachts. It is only recommended to browse data on local sailing areas as well as local meteorological circumstances. However, many experienced sailors also hire a professional local skipper when sailing in new and unknown areas, in order to have more relaxed vacations and enjoy sailing with fewer worries than usual.
If you are not confident with your sailing skills or you did your sailing exam recently, it is recommended to hire a local professional to teach you about local waters and regulations in ports and marinas. In such situation, it would be very useful if you consider your skipper as a tutor on your sailing trip and try to do as many maneuvers as possible on your own. This also refers to route planning and other aspects of safe sailing. Ask your skipper for advice and try to learn from him/her useful tricks and tips.
For those who have no sailing experience or a valid navigation license, it is strongly recommended to hire a professional. Professional skipper possesses a vast knowledge and experience in sailing techniques, maneuvers, route planning and onboard safety. Professional skippers are also educated in first aid and sometimes medical care as well. Furthermore, the skipper is able to mend typical damages on deck equipment, sails and an engine, as well as the electrical and other installations.
Last but not least, a good skipper is very well acquainted in the best spots for swimming and snorkeling and above all, in best restaurants and bars in the area. Good skippers usually speak at least one foreign language; they are communicative, cheerful and well behaved.
Sailing in new and unknown areas sometimes consider a dimension of exploring expedition and is exciting by a default, but hiring the skipper guarantees safe and a relaxed sailing trip for sure.
I wish you a calm sea, a fine wind and a strong mast!