I've had a lot of diesels over the years. A nice 7.3. a decent Duramax. And then I bought a Cummins. After working on them all, putting over 100k miles on each, there is really no comparison. The Cummins is vastly superior to work on in nearly every way. A bunch of posts on here... "My Ford has xx,xxx miles..." My last two Cummins I sold with over 700k combined. Never pulled the head on either. My current 2011 has 276k miles and not a rattle or squeak. I can change the Injectors on the side of the highway in under 3 hrs. In a Duramax or Ford it would take me literally 4-5 times as long. Same with water pump. Same with turbo. Mechanically both v8s are a flat out nightmare to work on. And the Ford 6.7 is the worst. And I would never, ever buy a Ford after how terrible Ford handled the 6.0.
I'm not arguing how each newer truck feels to drive. I've driven some really nice Ford's and Chevy's. If you aren't working on it, and don't mind more expensive repairs, then buy whatever you want.