[speeder]

I'd take an '06 Duramax LBZ w Allison over an '05 Dodge eight freaking ways from Sunday, unless there are some extenuating circumstances. You provide zero information about miles or condition, so I can't definitively say for the two trucks you're looking at but an '06/'07 LBZ is one of the best trucks ever made and an '05 Dodge is junk in comparison.

Cummins engines are great but they have their own issues and none of them matched the old 12v in toughness as they advanced in refinement. The problem is the truck they came in. Don't take my word for it, do a search here and on the rest of the web.

I'd say hands down that an 06/07 (old body style if '07), Duramax LBZ was the best diesel truck ever but the Ford 6.7 may have knocked it off that throne in my book. The '05 Dodge would be square on the bottom of the list.