I don't think there's really a question what UTV is the most dependable. The Kawi T4 is the Go-To when considering price and dependability.
If you want a go fast machine, a SXS is the wrong place to be looking. You can get a Dual Sport or a Sand Rail used for $5000-$10000 less than you would spend on the RZR. Your talking Acura v6, tons of leg room, and major whoop eating material. I think the prices have gotten a bit out of hand once the SXS's hit the $22,000 mark. There's simply better options at that price point.
If you have a Ranch and your a regular guy wanting to tackle the dunes, eat whoops and have a safe ride for the family in the $10,000 range, like me, then a SXS T4 is the answer. It will do anything a RZR will, including eating whoops, if you grabbed Rusty or Benchmarks new Suspension offerings. Your down 200cc but even that can be made up if you wanted too. My Benchmark 840 TERYX motor was head to head right with a RZR XP when I sold it and could keep up in the whoops like a boss with the HRT Suspension I had in it. We were all pretty amazed. I sold that T2 conversion for $8900 this month to make room for the new T4.