For 2000 the YZ was a 426, I'm not sure if the WR was 426 that year. The main difference was the suspension, which on the WR is softer for woods riding. Also it has the bigger tank, a coolant overflow tank, milder ignition curve, heavier flywheel, lights, and (I think) and 18" rear wheel. I don't think it would make a good MX bike, but is a good machine none the less. I have a friend who can beat me on the track, he rides an XR400 and I ride a YZ426, so the machine doesn't always matter that much. I think some people are just naturally fast. But for MX I think most would be happier on a YZ.