My brother has a '03 Rubicon, very nice.
I've used various Polaris machines for work and don't care for them; they don't seem to stand-up well.
I bought an Arctic Cat 500 in September and am pretty happy with it so far. Honestly, I think the build quality on my brother's machine is much better, but mine rides better, and is easier on fuel. I haven't noticed a difference in power between the two machines, but my brother prefers the sound that mine makes (he's usually following me). My machine has much better ground clearance, and the 2" receiver is nice to have for towing.
I could be wrong, but I think that Suzuki builds engines for Arctic Cat.