I have ridden the KDX 200 and 220, and have also owned a KTM 200 MXC. I originally wanted to get a WR250F, but decided against it after my husband read some reports on it, and from word of others. First, the bikes you are considering are very different from the KDX. Of course, I do not know what type of mod's you currently have on the KDX, however, if it is stock, or close to that--these bikes are much more pipey. I love the KTM 200, very very light, and can have lots of low end if you change the sprocket etc. Even when I was worn out I could pick it up. The WR250F is supposed to be harder to start and very performance oriented. I absolutely love 4 strokes--the power is very smooth, and the engine braking works great for downhills, however, there is the weight factor. When you are dead tired---will you be able to pick it up? Can you start it after you dump it? All things to consider. Good luck with your decision.