Having had both Ford and Dodge PUs while in the heavy equipment business, I'd lean towards the Ford.
The Dodge's Cummins engine is a bear...and God knows I sold a TON of equipment with them, from front end loaders to huge forestry equipment...but the tranny issues were many. Plus, the fit & finish of the Dodge can't compare to Ford's. With the Dodges I've had leaky cabs, rear beds mounted off center, dash and interior squeaks that drove me nuts, brake issues, suspension issues, tailgate hinge issues, etc. There were a few times when my truck brakes failed and I had to use the trailer brakes to stop the truck! Not fun as your heart is pounding out of your chest. They seemed to get old very fast...like after 50 to 60K of hard miles.
The Fords (F-250 & F-350 Dualy) I've had just ran...and ran...and ran. The engines & trannies never let me down while towing and the 4WD drive train was solid as a rock. Also keep in mind I serviced the hell out of these things because I had mechanics across 4 states at my disposal...so oil & filters were changed every 4K, tranny fluid and filters were always done before scheduled recommendations, they were constantly greased, etc. The Ford's fit & finish was far superior to Dodge's in my opinion...over the long haul...more things worked over time. The switches, door handles mechanisms, headlight knobs, the wiring harnesses that light up the dash & cab, tailgate hinges...all those little/big things that can drive you crazy just worked all of the time. I had wiring issues with a few Dodge trucks...keep in mind that these were work trucks that I drove on constructions sites with soft dirt, mud and snow.
A few buddies of mine had Chevy diesels and loved them...but I did hear some bitching about their rigs from time to time. The interiors were nice, but every time I rode in one I couldn't help but think it wasn't as nice and as comfortable as a Ford product....and I'm a GM guy. My all time favorite was an F-250 4WD Diesel with a standard 8' bed and a cab and a half. It wasn't too long to park in a standard parking spot, it had a roomy cab that I could fit a ton of stuff into, and it had power to spare when towing....and I exceeded it's towing capacity on MANY occasions!
Good luck in your quest...