I had a KDX220 when I was strictly riding offroad. It was a great bike. I now have a WR250R which is also great, but in different ways.
The KDX was much more responsive to a twist of the throttle, easy to loft the front wheel and throw it around.
The WR is heavier and more subdued, but still a lot of fun on the trails. It is also a decent street bike, which the KDX really isn't.