boat for windsurfer

I recommend lessons for windsurfing.  It's a long learning curve and lots are ging for kitesurfing instead as it's quicker to learn.  Don't buy a small board untill you are ready.  It's like putting a non sailer on a skiff to learn.  you will just get disheatened.  Get a high volume board and learn to sail the board first.  Then progress to harness and footstraps.  Ones able to do this you can then think about a smaller board for jumping etc.

Why are you changing from windsurfing? 

What you get sort of depends on why you want to sail?.

Frinstance .. I switched from board to boat cause a) the kids wanted to play, b) there was rarely enough wind for boards to be fun, c) when it's not board planing weather you have somewhere to sit down, d) boats seemed to like beating back up the lake better.

.. but even with the fastest highest performance dinghies. you don't ever get the feeling of raw speed and acceleration that a planing board provides... a single handed trap boat comes close though, if that's what you want.