I am 6ยด1" about 240lbs and have an 04 xr250. I ride trails and some sand pits mainly and I find the stock bike is a little underpowered for me but not terrible. It is quite agile, and reliable and pretty fun in general. I have taken it to the off road park where they have an mx track. I am pretty mellow on the track (i coast over the real high jumps). But, I have taken some of the smaller ones and it gets around pretty good. My suggestion is that if money is not a factor, go for the 400, anytime you can get extra power, take it. If u live in NJ you can check mine out before u buy one.