Polaris in general are heavier, couple inches wider, but generally a great ride. i have owned both Yamaha and PoPo's. I currently ride a grizzly. I can tell you that the ride isnt as smooth as the polaris, but it is lighter, much more nimble on wooded trails, and the drive train is solid. I just recently compared my grizz 550 and cousins Polaris 550xp and ride heigth was within an inch as far as clearance goes. His was 3.5 inches wider.
If you are thinking you'll use with passengers, the polaris' usually have a longer seat. Had to get my wife one of the big seat/box things as her a$$ was always on the metal bars of rear racks on both my last Yamahas. The polaris has a wider, longer seat.
just mytake on it....
Check out this website for great honest comparisons of used machines. grizzlycentral.com. My last one was a 2005 Yamaha kodiak 450. it had 3300 miles, some of those hard miles, and it was still in great shape with no issues.....I know of guys with 2-6000 miles and with regular maintenence, that shouldnt be an issue...Hope this helps.