I have seen no difference in traction with my 19.5's in a Toyo M608z vs the OEM Michelin LTX's, in fact the 19.5's are better in many aspects.
Many of my miles are off the pavement, so I have a good sampling of both.
I do run KM2's in 255/80R17 for my elk hunting as they do a little better in possible muck and snow, and the OEM wheels with the KM2's have better chain clearance.
There will, of course, be better traction choices for LT tires but I have been quite impressed with my M608z's. I have had them on snow/ice/mud/dirt/gravel, and the weight of the pickup combined with the torque is the biggest issue and not the tires.
There are many other aspects about a 8400lb truck, before loading, on a 1 ton frame that limit it's offroad travel.