My neighbor has a CRF450x and he is wrenching on that piece of crap all the time. I haven't had to do anything except normal maintenance to my WR450. I've rode his bike and it does feel good and easy to ride but he has spent a lot more money on suspension and stuff than I have. It's seems like he has to replace the valves every six months and he has already put a new piston in. That being said, here is my take: If you race or are an extreme rider and don't mind working on your bike everytime you ride then go for the X. If you like to ride her hard and put her away wet then get a WR450. She doesn't need much love to come out and play again.