It really doesnt make it that much more durable. Thats why they call it ply rating instead of actual plies, AKA Load index numbers. It is a little bit more durable, but with a good quality tire the sidewalls are usually the same which is probably the biggest off road problem area. Gdy Silent Armor and Pirelli Scorpions both have the same extra ply on the sidewalls whether or not its a LT tire or a P-Metric. BFG ATs dont make a P-Metric tire but the side walls are the same from load range C to E (6ply rating to 10Ply raing) Also when you go to larger sizes(larger than a 32" tall) there are some brands that have LRE's but most are LRD's especially the bigger tire you go.