TweetI was a dealership diesel engine tech before i started playing with cranes so i know a little about em. .
The Cummins is a the best engine of the bunch. The same engine you find in pickups is used in some pretty good sized medium duty applications. Very few problems with the Cummins mostly only a EPS sensor or a oil pressure sensor. They updated both sensors and harmesses so that problem should be fixed. They routinely go over 500k mi in medium duty apps with proper maint.
Between the duramax and the powerstroke the powerstroke is the better engine in the better truck. The duramax is a pain in the ass to work on. Maint costs after the warranty is up will eat u alive.
If you trade every cpl yrs and long term durability isnt a concern then it doesnt matter. Go with which truck u like better. Either engine will offer over a 100k of trouble free service. I am not sure whos winning the HP wars now i havent kept up on the brand new models. I do know in the last comparison i read Ford won every catergory and Chevy finished last in almost all of them.