Of the Hondas, you would definitely be best off with the Rubicon. It is "only" 500cc, but the overall package with the tranny, frame and drive system work very well together, and is plenty powerfull. When I had the Rubis they didn't have the selectable 2WD/4WD system, but they do now. Most utes are going that way.
If you plan to do a lot of submerged riding it pretty much counts Polaris out. I like their ATVs, and they have done a lot to seal the belt drive tranny. But it is notorious for being their weak spot. Polaris owners don't like to admit it to other riders, but they have problems when doing a lot of stream and/or mud crossings.
A lot of the new big utes are going more the way of the comfort/trail riding frame and suspension, like the Rincon. That doesn't make them bad, but takes away from the workhorse functions some. The new big Bombardier and Arctic Cat ATVs are very good in their own right, but are better known for their power and handling out on the trails and in the open than their work capabilities. Pretty much all the IRS models are that way - except the Polaris', but they still have that one weak spot.
With the Yamaha, you may want to look at the Big Bear, even though it is "only" 400cc. It is more hardcore worker than it's bigger brothers, and has the low gear as well.
As for the KawaSuzuki models, it's pretty much the same. The smaller one has the low gear, and the bigger ones are more geared toward the overall riding.
There are a TON of choices in the ATV world. I've stuck to Honda because I think their stuff is more solidly made, as well as the fact that I have a good relationship with a dealer.
I really think that the Rubicon is the best workhorse ATV on the market right now. It's not a bad machine for trails and overall riding, just not nearly as pluch as the current big bore IRS machines are. That said, the current big bore IRS machines are great at trails and other riding, and aren't bad at hardcore working, but they aren't quite as good as the true workhorse machines at that function.
Whew, that was fun. Of course, that's all just my :twocents: