The latest model HD gas V8's are pushing ~400+ HP with new 8-10 speed trannys. Late model diesels are also pushing ~400+ HP. 400 HP means they're both capable of doing the work. But . . . that tranny on the gasser will be constantly dancing around making up for the V8's lower torque on hills---not to mention that V8 pulling 3,000 - 5,000 RPM's while that tranny dances. If the sound and feel of this dance doesn't bother you, I'd go gas. Gas means less initial cost, cheaper fuel and less maintenance. If you're not fond of the V8's little dance, go diesel. Very few, if any downshifts with the diesel. As for the exhaust brake? Priceless!
