I have a 14 kx450 and 2 kx500 ,one in a 250 01 frame ,this is what I see the 500 is faster in area,s that are open to use 3rd to 5th provided there is heaps of traction and big hills the 500 will say goodbye to the 450,but if you have a tight hardpack track with lots of jumps the 450 is better .On a different note ,any one know what kawi is doing with there 15 models ,I see all the other brands info is out ,is kawi holding out on something special all just slow on releasing the information?