The diesel has plenty of power to tow, accelerate and pass..... Maybe a little too much. The gas motor gets the job done. I think the diesel is a bit overkill but that is the reason why we buy it.
When I drive on the freeway I can get the trailer up to 90 mph with the deisel. Is that a good idea. NO it isn't, especially if the CHP wants to crack down on speeding trailers.
I tow 7000 lbs and get about 15 mpg(Diesel) while doing the speed limit (its 65 right ). I don't think the savings will ever make up for the purchase price.
So it depends on what you want:
Diesel - good ol fashion American overkill
Gas- better value
Both are good trucks.