Im personally looking at a few different options:
2011-2012 cummins- They have better tranny and no def fluid
06- 07 6.0 Powerstroke with some work done, headstuds egr delete.
7.3s ride like crap with leaf springs in the front,
6.4 power stroke is a money pit and way worse than a 6.0
5.9 cummins always have horrible interior.
Not too familiar with duramaxes so Im going to be test driving them before I make a purchase within the next year or so.
As far as gas trucks, chevy wins imo for the best gas v8 and transmission, although I want to drive a 5.0 F150