I currently ride a XR400. I have been biking for years, but this is my first dirtbike. I've been riding off-road for about 6 months now. Two of the guys I ride with have YZ400's, and they are planning to get new bikes at the end of the year. I was thinking about buying one of their YZs to replace my XR. What type of performance differences could I expect by moving to the YZ? I ride in the sand 90% of the time. I have a really hard time keeping up with these guys, especially on hills and sharp turns. I'm sure riding skill has a lot to do with it too, but would the YZ help me out in these areas compared to the XR? Thanks.