All the same basic engine with changes to the fuel system, turbo chargers, and emission equipment. They are all interchangable, unlike the completely different 7.3, 6.0, 6.4 and 6.7. Just sayin.
I like all trucks, just prefer GM, I have to say Ford does do a good job in their fully optioned trucks as far as interior goes, anything 07 newer (6.4) look horrible, honestly why put the marker lights above the headlights?? Makes for one ugly truck IMO, the 06 down (previous body style) are alot better looking trucks. 6.7 trucks are just hideous. Lots of guys hold on to the fact that the Ford Torq shift holds more power stock than an Allison, who cares?? I know the 6.4's can make some good power very easily but they still can't compete with a Duramax that makes 100 hp less. They are heavy pigs!!!!
I suppose if I wanted a good workhorse that was reliable I'd buy a 7.3 PSD but none of the later engines.