We have a total of 4 Polaris Atv's and 3 of them have never had any problems and have been very strong reliable quads, and we have a 05 Sportsman 500, 05 ATP 330, 06 Predator 90, and now the Outlaw 525. They may weigh a little more but they perform Flawlessly.
I am hoping that my LTR-450 will have the reliability that the polaris's have had.
a lot of it has to do with the way you maintain them also. look at your other polaris' there is no way to tell them apart from new. the way you take care of your stuff I think a chinese quad would last forever. a lot of the polaris i have seen break down have been from runnin them hard and not takin care of them, any brand will do that though.