Silly comparison, really, as Gareth says we`ve done this one.
Sustained speed of almost 30knots over 24 hours in open seas, well you NEED a 120ft cat to do that. But Hey, even the VOR70`s are getting close to that now!
The difference is that windsurfers can go like hell for short periods, on flat or even choppy water.
We have a very informal series of speed events on a small lake in Cape Town, it gets very choppy, yet the top speeds (sustained over 2 seconds, I think) on GPS readings, are in the 40knot range, fastest sailboard was just over 40knots, a kiteboarder took the record with 42.03knots. Wind was 25-30knots. Now, these are fun events, not taken too seriously, weekend non-professional sailors on good kit.
PLEASE, PLEASE, PLEASE bring a Hobie Tiger, Tornado, Inter20, whatever you think can do that speed in 3ft chop, 25-30knot very gusty winds. Just let me know you`ll be there, I`ll bring video camera. (Don`t bring Orma 60, lake is only about 200m wide !!)
It doesn`t matter which is faster, we are all having a complete blast at whatever the design limit of our craft, ask an Optimist sailor what a rush planing down a 7m swell offshore Durban can be.