What's the big difference's between the two? I know you get the 6.0L vs the 5.3L when you jump to a 2500hd, but at would it before worth the loss of fuel economy? A buddy and his brother both have 2500's with 6.0's and the best they have managed are 14 mpg on longer road trips. Another friends parent's have a couple of 5.3L regular cab stepside Chevy and GMC trucks that have hit 20 mpg before. Would it only be worth getting a 2500 if you plan on hauling heavier stuff or do they ride a lot better during general driving also?