In regards to off-road capability, I guess it's all relative to what you are comparing it to. As somebody who has ran highly modified off-road rigs (everything from quads, SxS's, and fullsize trucks) I will say a stock PW is just average, or maybe even marginal. I've ran a Chevy K5 Blazer off-road for years and it has progressed from 33" tires and limited slip front and rear diffs, to 35's, replacing the rear limited slip with a locker, replacing the front limited slip with a locker, going to 38" tires, and then 40" tires. I will say that the K5 on 35's and limited slip diffs would out perform my PW on 37's in 9 of 10 conditions. Most of that is because of the much heavier weight and the overhang/ground clearance of the PW. The only advantage in some situations the PW would have is it has more power and a longer wheelbase which helps in some situations. Compared to the K5 with 40" tires and lockers front and rear there is absolutely no comparison.
Now a stock PW compared to a stock regular 2500 is a decent difference in off-road ability......but still only so many places a 7k+ lb. fullsize truck on 33's can go. I do think that going from a 33" to 37" tires make a pretty big difference. 2" of ground clearance may not sound like much, but it makes a big difference.