Between myself and family, we have a bunch on our place. I own the 590IS4 gator, otIhers are two Kubota RTV 900 Diesel, kawasaki mule, and two rangers. All of them have their place and perform better in different areas. Overall may be biased, but I'd take my gator or the ranger over all of ours. My gator does everything I've asked it to do and more. Great ride, and plenty of power. I will also agree on the power steering, it's AWESOME!! The Kubota's are great for hauling stuff and will pull just about anything. Ride isn't great and even though our tractor is a Kubota, they hydraulic drive is annoying. But they are a work horse. The Mule is ok and gets most of the job done, but it's underpowered and doesn't ride as good. Overall not bad. The rangers are like the rest of them out there, some good, some bad. So far, the ones we use are good with the occasional breakdown, but nothing too major with the exception of the axle shafts. Now, my neighbor has one of the new mules w/power steering and it's pretty nice. One of the ranches we guide at got the new Can-Am and that thing is NICE!! Don't have much experience with it though, but from what I've seen, it pretty damn nice.
My choice would be Gator, Ranger or Can-Am with Mule following and Kubuota last (unless you pull trailers and haul heavy loads, then I beats them all)
If you buy a Kubota you don't need to worry about warranty. They never break or wear out.
We've got two of them that I will disagree with you on that.... several times...... Axles, front drive shafts, overheat, fuel pump, and few others. It's a workhorse though.