The 5.3 and 6.0 are both good engines. I wouldn't make my decision on the engine, they both have enough power to get to where you are going. I have a 2012 6.0 and I am satisfied with the power and towing performance. It is on the thirsty side 12 mpg mixed city, 16 mpg highway, 8.5 mpg towing 8k lbs.
I have had both 1/2 and 3/4 ton and the 3/4 ton truck can handle a lot more load/trailer than the 1/2 ton. From the sounds of it you use a truck like a truck and need one that can handle some load.
A 1 ton srw would also be an option to consider, it would be basically the same as the 2500 but cost a few 100 more and able to haul a few 100 lbs more.