Just to help with the confusion.
I just had a costumer in the shop with rv brake problems. There was 2 guys traveling together they were on their way to alaska. Retired couples not hot roders. They both had 07's 5. 9s one had a 2wd 3500 dully cc auto long bed 3. 73 with a slide in camper. The other has a 4wd 2500 cc auto short bed 4. 10 pulling a 5th wheel. They said the truck pulling the 5th wheel has always gotten 1. 2 to 1. 5 mpg better. Go figure.
I would still buy a 2wd, but I agree you only need 4wd once to be glad you have it.
If you are going to buy it to pull, set it up to pull 4. 10s.
04. 5 3500 4wd cc dully 6speed 373 50k
93 2500 2wd xc auto 354 250k