The ISB Cummins trumps the Isuzu Duramax in every way except a mild bit of power but it doesn't feel any less strong. The New 6.7 will trump them all. 6.0 Superduty's are fun trucks, but the reliability is really poor. As for Chevy, I thionk they're pretty boring rides with about the poorest interior fit and finish around not to mention the number of TSB's issued (second only to Ford for SD's head studs and gaskets). The Allison is nice, but the New Asin in the Dodges will be more than a match when you factor in the low cost availability of a factory exhaust brake and Tow haul features nearly identical to the Allisson. As for looks, Ford wins IMO, but Dodges look great with armor too. Chevy, again, just a plain jane looking rig (wich can be good sometimes too).
If I had my dream Fully/Camping/Tow rig, I'd get a Mega Cab std bed Cummins HO equiped 6sp manual Dodge no questions asked.
I drive an 05 Superduty for work and I really like the size of the rear seats and the utiliuty of the thing, but as hot rod as the motor is, alot of little things are gong tits up on it after not alot of miles (like 30k). It looks great espescialy on teh 35in MT-KMs and the Manual is nice since it in typical Ford Fashion has a granny first (awsome if you've got a load or a big trailer on) but it's ALOT clunkier than say my uncles manual Dodge.
I've only driven an Auto Shiv, and since I really dislike the disconected feel of slush boxes, it really didn't appeal to me. The motor is powerful enough, but it doesn't feel like the snorty grunty diesel's in either the Ford or Dodge, and I'm a realy sucker for a Cummins with a straight pipe, they sound like dump trucks/big pieces fo heavy machinery. Not to mention the Dodge with a Manual feels like it's a 5 ton ferrari when you get on it, same with the Ford they're fun too.
Cheers
Dave