Ltr 's are known for breaking gears, 04-05 trx450r's are known for a bad batch of crank bearings because they changed bearing company's right before the 05's. The yfz's are a good platform but are very uncomfortable. My 2 picks would be the yfz or trx. The other ones are slow except the Ltr after alot of mods. My 04 450r beat all of them no problem. Honestly I wish I wouldn't have traded it off for the banshee because I beat the shit out of it and it never missed a beat and I have worked on the banshee alot more than I have rode because of all the bugs from the previous owner. Lol