I have a 2011 2500HD GMC, I liked the pushrod V8 for reliability and the drivetrain of the Chevy is solid.
I was recently considering going the diesel possibly dually route and converting to the camper forum (I still would have if I had the $$). I test drove all 3 brands with my order of preference going into it being Chev, Dodge, and Ford.
I found Chevy to be awesome with the duramax, but payload was lacking (the price of an indy front-suspension), the ride was awesome.
The new Ford powerstroke surprised me and the dual turbos and the best get-up-and go, it literally felt like a V8 gasser. The downside to Ford was the interior ergonomics seemed to be designed for people under 6' in height. Everything looked sharp, but was wrong. Felt wrong, in the wrong spot.
Dodge was the biggest surprise between utility and capability. The new interiors rock compared to previous dodge iterations, the crew cab foot well coolers are awesome, and the Ram designers have put storage in every possible place they could get.
At this point in time, I think all 3 make extremely reliable pickups. Test drive all 3 and find which has the best price combined with what "feels" the best for you..