What kind of riding? I own Polaris ATVs. I think if your getting a deal jump on it. If not look that that new 450 suzuki just came out with it has a lot of nice features. Gotta say: the 700 King Quad is definatly worth the money from what I have heard.
If you are looking for a true 4x4 (polaris has AWD instead of the usual front limited slip) machine that has a extremely cumfy ride and is reliable... get a Polaris Sportsman for sure. A close friend just bought a 800EFI and I hear that things a BEAST.