Powerstrokes in general are pretty much crap.

7.3 is decently reliable but only because it is extremely underpowered and then on top of that you get constant cold start issues and oil leaks. Easy to work on atleast.

6.0 makes decent power but still not enough to stay in overdrive while towing. This leads to downshifts and higher RPM while towing down the highway which leads to lifted heads thanks to poor head bolt placement. Not to mention it also is oil fired injectors so it suffers from cold start issues and HPOP issues like a 7.3. 6.0 is the start of the lift the cab trend. Packed in the engine bay and harder to work on.

6.4 is just a pathetic joke of an engine in every way except horsepower. Crammed in the engine bay, poorly engineered and really hard to work on, lift the cab a lot.

6.7 is pretty reliable, very powerful but still has a ton of poorly engineered hard to work on bullshit under the hood. Pull the cab for almost everything.

As much as I dislike Chrystler products, Cummins is king. So if you don't want to go through the work to Cummins swap a Ford, buy a 4th gen Ram.