I do not drive a diesel now but I would not be looking at the engine. I look at the drive train.
The Cummings is more expensive to repair but less likely to need repair. The PowerStroke is more likely to need repair but at less cost. The transmission in the Dodge is stronger than the Ford if you are going to haul over a distance but will cost more to repair if it goes bad. The Ford is not as strong but if your primary use is just to move the vehicle driving on the roads and interstate it will serve you well.
So if you are looking for a vehicle check with the tranny shops and the independent diesel mechanics for the up to date info on engine and tranny strengths and weaknesses.
"The Second Amendment is not about duck hunting, and I know I'm not going to make very many friends saying this, but it's about our right, all of our right to be able to protect ourselves from all of you guys up there." - Dr. Suzanna Gratia Hupp, appearing before Representative Charles Schumer's committee hearings on the assault weapons ban