Well, now that the Cummins 600 is 50 state legal, it may well be set to take the lead in diesel unit sales of the big three.

Dodge had done badly in California sales in comparision with Ford and GM, apparentely because the only Cummins available there was definately outclassed in HP and torque by both the PSD and the Dmax.
But now that the 600 is 50 state legal for emissions Cali buyers get the same power ups as everyone else does, and the Cummins has actually surpassed the Dmax in California sales for the first time since the Dmax debued. It's closing on Fords Powerstroke numbers every day- even as I type this.
Considering that California represents the largest new vehicle buying market in the country, it's entirely concievable that the Cummins will become the number one diesel in America if this pace keeps up.

Dosent surprise me really, you can say all you want about the quality issues concerning the Ram(though I like them) but anyone who seriously doubts the quality, and durability of Cummins engines,while supporting Dmax or PSD engines as being the "best", has some serious credibility problems as far as I'm concerned.