I frequent RV and Travel Trailer forums and have read positive attributes to using gas or diesel engines. These were points that were brought up by both Casual Campers and Full Time RVer's.
Benefits of diesel :
Diesel will get better mpg towing and empty.
Diesel has more torque at lower RPMs.
Benefits of gas:
Gas costs less per gallon.
Although a minimal cast, you don't need to run DEF fluid.
If an engine has trouble while you're traveling the back country, you're more likely to find someone who can work on a gas engine versus a diesel engine. Diesel mechanics are more expensive than gas mechanics in my area.
Then you have maintenance to consider. Maintaining a gas engine is usually cheaper (fewer filters etc..) The 3.0 Diesel has a belt that needs to be changed at around 150,000 miles (someone please correct me if I'm wrong).
Some RV forum members also mentioned the payload of their truck was less with the diesel engine because it was heavier. If true, this would hinder your GCWR or Gross Combined Weight Rating(the total weight of your truck and trailer loaded with gear and passengers).