My first truck was a new 75 Chevy with L78 15's, that size was better in snow, on road, but when I put 12/32 15's on I could go places in loose dirt, sand and mud the L78's could not go. I keep the smaller wheel/tire combo, but never felt the need to go back to the smaller tire for what I do most of the time.
There are various factors in play, the weight of the vehicle and the diameter of the rim as well as tire size, look at those old Model T's going places today's vehicles would probably need 4WHD.