Radial outlaws hands down !
From what he has said, I dont think those are the tires for him. They are just too heavy and possibly too agressive.
Bighorns are great all around tires. I'm going to pick up a set of 28s for my 900 soon. The 26s were too small for my taste and just didnt look right. A lot of the guys on the RZR Forum swear by the Pitbulls, even over the bighorns, but they are heavy. Also from what I have read, the Moto MTCs are also good all terrain tires but they are also heavy. I picked up a 28x10x14 Moto MTC and I swear it weighed more than my 26x12x12 Bighorn Mounted on a wheel.
BTW For such a small tire like a 26 I'd stick with a 12" rim.