Which one is better for a cruising sailboat?
The answer is both. In the winter (North of the equator) the winds are stronger and the sun is lower in the sky. In the summer, the sun is more close to overhead and produces significantly more energy, and winds are weaker. Local weather has the effect of causing little wind and bright sun when there is a high pressure, and clouds and winds during weather “events”.
Wind can make enough energy for a typical boat, if you are in a place that is windy. You can find a map showing wind resources at: http://www.nrel.gov/wind/international_wind_resources.html or other on-line resources. Also pilot charts show the wind speed and are available at: http://msi.nga.mil/NGAPortal/MSI.portal?_nfpb=true&_st=&_pageLabel=msi_pub_detail&CCD_itemID=106&pubConstant=APC
Generally speaking, North of Chesapeake Bay, the southern Bahamas, Greater Antilles, Eastern Caribbean, and North coast of South America are very good in the summer, and just about anywhere in the winter.
However, much of the time you will want to be anchored in the lee of the land, in a protected anchorage.
Solar can make enough energy for a cruising sailboat, if you have enough room for the panels. A typical cruising sailboat uses about 150 amp-hours per day (Ah/d). In order to make that energy, you would need about 450 watts of solar panels. At about 15 watts per square foot, you would need 30 square feet of solar panels. Difficult for a monohull.
Having both can make it possible to make your own energy without having to start the engine or generator.