The numbers on these newer trucks is amazing. I couldn't justify buying a diesel for a weekend hauler. Hell, you even see these guys doing hotshot with gasser trucks now. Sure a diesel will out perform them, but who actually need 500 horses and 1,000 foot pounds? You see these guys pulling these 10,000 pound campers all over the US with half tons.
The Ford and Chevy drive completely different. Going from a bare bones chevy to a lariat Ford are not even close to being in the same league. He needs to drive them and find which one he likes better. The chevy rides smooth, Ford rides like a truck. Ford will never rust if he is looking at the newer aluminduty. I also thunk the 6.7 is the superior of the 2 diesels. Gasser I would go with the 6.2 over the 6.0 but I'm not sure about the newer 6.6. Adam seems to continually be impressed by his.
In the end, it is all about comfort. He needs ass time. If he doesn't like the way it rides, he won't keep it. They are all plenty capable. Some just do better than the others in different areas. Like fitting in a garage, turning in the grocery store parking lot or overall comfort. If he is looking to do mods, these are also different by each brand.