I've driven both and I would call it six of one and a half dozen of the other.

Don't say that there have not been 5.9 Cummins go a million miles until you have some firm data to back that up. I've never done any research on it, but I would be SHOCKED if there aren't a number of them that have made a million miles. I sure shudder to think about how bad the cab rattled at that point though. The worst part about driving a Dodge pick up is that every time you slam the door, your first inclination is to roll down the window and look out to see what fell off.