My 2 cents on diesels......
GM dealer mechanic so I'm somewhat biased going in. That said GM's Duramax is indeed mostly designed by Isuzu in partnership with GM. It is the quietest smoothest diesel I've encountered and there is special programming for emergency vehicles to squeeze out even more performance. Mated with an Allison trans it's tough to beat on reliability.
Ford has had many problems with it's diesel designs and change them frequently. I hear good things about the new ones but the 6.0 had problems.
Dodge of course uses a Cummins Diesel that is well proven and a torque monster but horsepower was never the goal. Just don't order at a Drive Through without shutting off the engine.
Dodge's weak point I believe is their trans and needs to be beefed up to match the Cummins.
We all argue about whose better but all these trucks are running the roads every day and Mechanics like me will never run out of work on them.
Don't get me started on Toyota and the way they deceived the public on reliability.