as someone who has owned both a 6.0, and a current 7.3 owner i gotta say 7.3. i've only had it since january when it had 109k miles. now it's got 154k, and no problems. the transmission was toast when my best friend signed it over to me. that and a cps is all thats gone wrong with it other than regular maintenance. i think nothing of taking it from jersey to california every few months. while the cps does go out more times than not i don't think there are as much of a variety of problems as there are with the 6.0. the 6.4 sounds like it's got it's fair share of problems too which is never good when you buy a $35k-$40k dollar truck. whether it's a free warranty repair or not. my 6.0 did really good, and i disagreed with all the naysayers. never had any warranty work or anything. once i got to 83k the egr gave me problems, injectors, blown piston in the motor, wiring harness. after that i got rid of it.