I raced a lot of XC type races on my 400EX and beat a lot of 450R….however one place the 450R shines is open stretches, they will pull away and make passing more difficult. My son raced very good on my old Race 400EX but then moved up to the R and that same year won the Quad B championship here locally. If your serious about racing, as much as I like the 400EX I would recommend you step up to the 450R, your going to end up there anyway sooner or later. Best wishes to you racing….