OK, so heres the deal.
The diesel will get way better mileage and will likely be much cheaper to own in the long run....or will it???
Every time I have a stressful day, all I have to do is go for a ride in my truck: the odd rumbly sound of the Viper motor on start up, the force of acceleration onto the highway on-ramp, the unique howl of a V-10 at red-line, and the beautiful sight of my speedometer sweeping past 100 mph before it even shifts into overdrive....
You just can't get that in a diesel. At least not for any reasonable amount of money. Think how much you will save on therapy, and antidepressants. Plus, once you are a pharmacists, the last thing you need is to be tempted to sneak on over to the narco shelf and help yourself just because you are feeling so distraught over having bought the wrong truck.
So just tell your sweetheart that you need to buy the Viper truck in order to stay out of prison...
Oh, and like the others have said, be prepared to do some upgrades and mods on the automatic tranny. But, it's basically the same automatic tranny that is in the Dodge diesel pickups, so I call that a wash.