Diesel Bombers - 5.9 Cummins or 6.4 Powerstroke

I have my preference but I won't say but I got food for thought.
What is it that you will do with it? Is the big question. Are you pulling a trailer often, just a go a to b truck, or make it into a power horse, or is it going on dirt roads.?? Because depending what you want to do with it can help determine what to get, cause both trucks have flaws in different areas.
So here's what I have to say for both

Ford: 6.4l are pretty reliable but up to a point unfortunately generally after 120k miles especially when it's running a tuner or even worst if it had a h&s tuner where problems come and severe too (And tuners definitely reduce the trans life to) If it was stock all its life should be able hit 180k miles without to many problems but not always the case for some. And they are costly to repair and a real pain the ass to work on. If your a work on my own truck of guy, I would avoid this one. But it has amazing power though compared to the 5.9. So power is definitely better power especially in higher rpms. But it's the truck itself that is the winner, they are more sturdier and tougher, so if there s lots of dirt roads, this is the one you want. Also for a trailer, a hitch type this one will be better too. But 5th wheel both dodge will be ok but the Ford is a bit better. Trans are pretty good and it's 5 speed auto compared to the 5.9 4 speed auto. But one thing is a big disadvantage is it has the emission crap (both dpf and egr) where 5.9 doesn't have these, big plus for dodge

Dodge: 5.9 tough motor and easy to modify without to much sacrifice on the motor as long you treat it right (egt s, power level, etc) and if anything happen to the motor, much easier to work on and less shop expense also. Upgrading the fuel system can real help injector life which they can have premature problems. If modify this truck can kick butt power wise and great mpg. But it's the truck itself that is a bit of a bummer, front end problems are common butttt can easily be replaced for upgraded parts. And also trans can be a problem too, but problems come from neglected maintenance. (Recommended service around 20k miles with oil & filter change (flush only on initial but afterwards no need) and trans band adjustment and using amsoil as oil brand) maybe hardcore but you can really avoid problems premature failure. But also some have done valve body upgrades and torque converter, which also really help. But personally trans and front end work I would prefer to take on more the engine (especially comparing thé 6.4) And truck body integrity really isn't the best, Ford has the upper hand. So this truck on dirt roads can get beaten up (if front end is stock) but on pavement both truck will be fine. But if You do everything Right this can easily hit 320k mile on the engine and can be a great hotshot truck too.

So hope this info helps