IdaD wrote:
The heavy gas trucks do get terrible mileage, but that's offset at least some by the cheaper oil changes and the fuel filters you have to do on diesels. And the 6.4 supposedly does a little better unloaded because it has cylinder deactivation. Still, you're definitely going to be paying a bit more for fuel.
A more practical difference between the two might by towing range - with the gas truck, you're going to need to be more careful about planning for fuel stops and you'll be stopping more often. You live in a more populated state, but if you plan on traveling out west that becomes a bigger factor. Just something else to think about.
Edit - go drive both too. Some just flat prefer gas or diesel. On the Ram, the 6.4 and CTD feel like very different trucks from the driver's seat.
Yes the 6.4L Hemi gets less mpg than my previous diesel (5.9L Cummins), but I certainly wouldn't call it "terrible". I have no experience with the newest crop of diesels, but from what I have read, they are gaining back some of the huge mpg hit they took in 2008 when the DPF was added - that mpg was terrible LOL. DEF seems to really help, though it is an extra thing to worry about.
Towing range is also correspondingly a little less with the Hemi when compared to the Cummins I had.
I have a few videos of my mpg and I have tracked it a number of times. Mpg stories are like fish stories though, so I prefer to use video evidence :).
See for yourself....
Here's a few videos of performance and mpg 
