I love our 2015 2500HD denali cc/4x4/sb duramax. Gave our son the 2004.5 silverado duramax cc/4x4/sb with 130K miles on it, will probably go another 200K. had Zero issues with the 04.
Love the 2015, got it in March and already have 11,000 miles on it. Better mileage than the 04 when running empty, and san diego. Towing mileage is basically the same as the 0.4
I will agree, 2500's don't have a lot of payload, mostly due to the class 2 GVWR limit of 10,000lbs. Take that and 4x4 and diesel and crew cab, and payload isn't that high. We would have gone for a SRW 3500 virtually the same cost, but rare as hens teeth on dealer lots. Some 3500SRW long box, but few short boxes. To me, the 3500 rides very close to the 2500 when empty. 3500 does have a second overload spring on top of the spring pack, 2500 doesn't.
Our son has had dodge, ford, and GM 3/4 ton 4x4 work trucks. his preference is the GM. Personally I like the GM IFS over the other with SFA, but in reality all 3 mfg make very fine trucks.
Drive all of them and pick the one that YOU like the best and best fits YOUR needs.