I haven't ever owned a diesel pickup, but I have been around quite a few, and heard of the repairs. Yes, I am biased towards GM, but that doesn't mean that they are perfect. I believe that the 6.7 Cummins is a pretty good engine, even though, from what I know, it doesn't have an actual Cummins cylinder head. But I am not a fan of the Ram body and I wouldn't have faith in the wiring or some of the suspension components.
A Ford, no way in my opinion. The things that I have seen people go through with them, the stuff that I have seen on YouTube, the crap that I have heard of from repair technicians, no... way.. The wiring fiascos that i have heard of. A blind spot monitor module will screw up power windows on an F150. The bosses Dad found that out. He cracked the lens on his taillight, didn't fix it soon enough, then it cost $2K for a module and taillight, and he still had to wait a month to get it reflashed.
Heck, I have heard that the dealer here is a month out on all repairs. They have so much stuff broken that they are stacked up that bad! In the meantime, my wife's little Buick had a purge valve goof up. She took it in the day after she called them, they ordered it and she took it back 3 days later and got it replaced. Less then 2 days downtime total.
Anyway, as said by others, plan on fuel system maintenance, I recommend a good fuel additive that adds lubricity. I use Schaeffer's for the fleet at work, my son uses it in his Dmax.
Solid front axles don't seem to be that great in the late model stuff. Ford has a reputation for having death wobble even at low mileage. I heard of it happening at 8K on one F350. All makes need components replaced eventually, more often with oversized tires.