Hi all!
If your looking for rash vests for the winter, best to buy a titanium lined vest. They are super worm, and can be used with a pair of board shorts in the summer.
Single layer suits are Ok for windsurfing as the water runs of very easily. However single layer rips quiet easily. You would be best going for Double layer construction, just in case of the drag along the beach sindrome, also some knee pading. You can buy suits which are made of both single and double combined. Normaly the single layer is around the Body area. These give the best of both worlds.
Good Hunting!