It depends on a few things, for both gusty conditions are difficult for beginners (maybe a it harder for windsurfing).
Water depth is another, water-starting is easier with a kite.

There are lots of places where they give kitesurf lessons in very strong winds (30kts), you just use a smaller kite.
Before going out on the water students get to learn with a small trainer kite to get a feel of how to steer, and the first time out on the water is without a board anyway.

Pete: You really should take a kitesurf lesson as well, just for comparison.