Just this summer I upgraded from a 04 1500 EC 4x4 Silverado with 5.3L, 3.73 combo to a 2012 2500HD 6.0,3.73 combo. Pulling a 7k trailer with both. The 1500 worked really hard pulling around southern Ohio..The 2500HD makes it very comfortable towing. Mileage..I was getting around 16mpg in the 1500 and I am around 13mpg in the 2500. Also a big one for me is trans temps. I put a large cooler on the 1500 and 175-190 was the norm 200 on a hot day. The 2500 trans temp stays 160 when towing..granted I have not towed with it on a 90 degree day yet.