I had a 2012 sierra, with tow pacage, and went to the 2000 6.6 gasser. Much better in all aspects for a TT. The 1500 can tow it, but it wasnt fun on ling rides. I think the variable engine stuff effected the performance of the older truck. So there was a delay from the cylanders after stepping on the gas. I think some bypass it, but i just got the 2500. Other stuff is the larger gas tank, so while not much better mpg, you will stop less as the 2500 tank is huge. Stability wise is better also. I was at 60 mph to 65 depending on the roads with the 1500. Now 70 is np. Grades are much easier also, 1500 on large grades with the petal pinned, i had to move over to the truck slow down lanes, with the 2500 i can pass at will. My camper is 4500 ish dry , so 5500lbs packed. And the bed of the 2500 is larger, so you xan load up more ****. Hope this helps.