I've been a windsurfer for 20 years and a kiter for 1. Curiosity and peer pressure were killing me, so I just HAD to try kiting. Now I like it so I'll probably keep doing it, even though I sometimes question whether it's worth the hassle and the extra danger...http://jimbodouglass.blogspot.com/2010/06/wax-and-feathers.htmlhttp://jimbodouglass.blogspot.com/2009/09/wind-thresholds-and-kitestration.html
When it works, kiting is easy and fun, but things do go wrong a lot more than they do with windsurfing. I have had more gear problems and breakdowns, done more swimming and walks-of-shame, and been skunked because of weather more often in one year of kiting than in twenty years of windsurfing.
I haven't had any serious injuries yet besides getting the skin peeled off my finger in a stupid trainer kite accident...http://jimbodouglass.blogspot.com/2009/09/wind-thresholds-and-kitestration.html
But there's no doubt in my mind that kiting is a lot more dangerous than windsurfing. In windsurfing when you lose control you lose power, but in kiting when you lose control you can still get a crazy surge of power from the kite. The modern bridled kites with their depower and safety systems only partially help. 5 line is the safest depower system, but if your kite inverts and powers up, the 5th line can slice it in half.
I think the main thing for safety is just to get familiar with your kite like a pilot would with an airplane, and ride cautiously, avoiding conditions you're not sure you can handle.