You shouldn't guess.

I have lived in and driven extensively the mountains of Colorado and Washington, mud and clay of Ohio and Texas, and never once wished I had bigger, wider or blockier tires.
Usually, I was passing or pulling out the macho trucks (think red, liftkit, calvin/hobbs, NASCAR reference, scrotum from the hitch).
Look at the people that drive offroad for a living....Colorado highway patrol trucks...pizza cutter tires with small treadblocks/siped.
I will continue to cover the backcountry with my Michelin LTX AT's and have a jerkstrap for when I come up on you.
Wish I had a picture of the two Toyota Boytrucks that I passed in the mud with my little soccer mom GrandCherokee...it was like they saw a ghost.