Hey, I have had both the YZ250 and WR450, I currently own the WR450. It really depends on the type of riding you do. The YZ is a great track bike, with great speed and handling. However, it was tough to ride in close quaters like trees and boulder sections. It also struggled pulling hills... not for lack of power but because it would lose traction if you reved it too hard and if you slowed down you risked stalling. The WR is a great trail bike that pulls hills like a tractor and is great in the technical stuff. It has decent power and speed, but nothing like the YZ. On the track The WR would get lapped without major mods. I don't have much experience riding sand, but I would think that the YZ may perform better becasue it would get you planned up on the top faster than the WR. I hope that helps.