The 3FE inline six in the truck, with a whopping 155 hp for a 6K pound truck is a tad anemic in the power department, so I didn't want to turn bigger, heavier rubber. Additionally, I really haven't found that for my type of wheeling (travel) that I've needed larger tires.
The 31s are easy to work with, roll around the garage, or lift up to the roof rack, and they're available at every llanatera (tire shop) in the middle of BFE.
As for mud terrains, I will always go with the BFG MTs (unless I can find a good supplier in the states for Michelin XZLs....). I have run through 6 sets of these on 3 rigs, and they've always performed flawlessly. The BFG MTs are made by Michelin, have a lower pressure rating (emergency) than the XZLs, and the sidewalls are fantastic! They're a tad overkill for the street, but the extra traction is there when I need it, so the trade off is worth it.
In several thousand miles of Baja, I've never had a flat or slow leak!
What's the old "hot rodder" saying..."If it doesn't have to work, chrome it!"
I hate chrome...
-H-