Which Differential for Truck Camper

Thanks for all of the input. I should add some color commentary that my wife and I are in our early 60's and plan to keep this rig through our golden years. We don't change RV's often having recently sold a tent trailer that we had for over 32 years. The last 20 years or so we have camped out of both a truck camper shell and a cargo van taking the tent trailer only for long weekends and longer vacations. This rig will be a major move up for us amenity wise. Back to more topic related information, the truck will be dedicated 95% of the time to the camper for at least another five or six years as I have a company vehicle for daily driving. After retirement, it may see more around town use. The 4:10 sounds like the better way to go given that most trips involve the Cascades and Sierras. My need to pass everyone else on the road faded years ago, one of the factors leading me to gas over diesel and with a camper, wind resistance will be the MPG killer more than gears I suspect. I enjoy the input!