I was in the exact same boat . I ended up buying a like new rzr 4 900 with a ton of upgrades, even after the purchase i was still wondering if i made the right choice.
Most of my riding will be around my house with my wife, and my 5 yr old . So the tyrex seemed like the best choice, but i bought the rzr instead.
It was definatly the RIGHT decision for me. I took the RZR stony lonesome and it did awesome. I rode with several other SXS including a ranger and a tyrex. There is no comparission of the two. They are in different classes . The tyrex seems to have enough power to ride at a good steady pace and seemed to be decently stable. The tyrex and ranger are more compariable units.
As i was told while i was trying to decide the tyrex is like a 4x4 pick up and the rzr is like a well tuned 4 tuned race buggy. You can still drive the rzr slow and with the family , but when ever you want to get your blood pumpimg the rzr is the real deal . Riding the rzr kinda reminds me of riding a dirt bike. THe rzr rides so smooth my wife and her friends have even comemted on it.