It's interesting to note that for the 5.7 and comparing the gear options, that yes you do get another 2,000# to tow, but here is something to think about and not sure how RAM figured this in but:
Granted you can get that extra 2,000#'s moving, but how are you going to STOP it?
Perhaps there are bigger brakes on that, but I'm thinking its all the same or at least not aware of it.
I look at it this way. sure getting up the hill will be easier with that weight, but at some point you have to come down that hill.