http://www.thumpertalk.com/bike/ubb/ultimatebb.php?ubb=get_topic;f=3;t=009730
It's pretty hard to put a finger on which bike is best (KDX or WR426F). I have both and both run trails well, climb hills great, and roost up a storm.
The 4 strokes are making a comeback, YAMAHA is doing a great job. Kawsaki's KDX is simply magic! Mine is all stock and is still a great bike.
My WR426F has been modified exstensively and is fun to ride. If you just wanted to buy a bike and go ride the trails, then go with the KDX.
The seat on the KDX is more comfortable. The WR has one tuff suspension. Both are 02 models.