After driving the 2013 400/850 RAM yesterday and hearing what people think of their new Fords or Chevys, just go by the one that turns your crank.
To me, having owned two Dodge/Cummins, a new one will most likely be a new RAM. It still uses the reliable Bosch CP3 injection pump, which to me is a big plus verses the Bosch CP4.2 that the other two have! But that is just my personnel preference, as I have never owned a vehicle that needed to be in a dealers shop often. So I am not ready to subject myself to that possibility!
Chris