i gave 7128 for 06 trx450r w/ es and hrc installed, i couldnt be happier. the other 450's are all competitive to the point of the rider making the diff. you should also see what you want to do with it ........trails, sand, drag race, etc the raptor has reverse for woods/trails. the yfz handles really well (if you push it hard). the 450r is honda so reliability is unquestioned. the 500 pred. is also in the running. sooooooooooo many choices and really not a wrong one (but one may be slightly better for you personally and what you want to do with it) sit on them, test them, and buy the one that fits you best. I honestly think you will be happy with any of them
2006 trx450r
2006 yfz450
2008 400ex
1999 400ex
2008 250ex
2011 rzr S