Lloyd, when I was looking for a replacement for my 2000 Mule 550, the Teryx wasn't out yet. I test drove the Mule 610, but for the extra $ found the Rhino 450 to be far better for my needs. Tested a Ranger and liked it, but the reviews I was reading turned me off. If I was looking to replace the 2006 Rhino today, the Teryx is almost certainly what I would go for. The RZR isn't utility enough for what I need at the ranch so it hasn't even been a consideration for me.
Buckskin, it's nice when you get a good one that lasts, no matter the make or model. I have had good luck with Kawasaki and Yamaha.