My "newer" pickup is a 2009 Chevy 3500 crew dually with 6L gas engine. It carried my 11' (main floor length) Lance camper (weighs 4,000# with groceries, clothing, and bedding for two) nicely to Alaska and back two summers ago. Around the Dakotas and MN, it carries the camper and tows my 17 1/2' boat while carrying the camper. If I had a 5th wheel instead of a pickup camper, I'd have bought a diesel.
The big downside of a diesel, according to a Ford shop foreman, is commuting with one will damage the engine prematurely. He explained that any time you start a piston engine, the cold rings let fuel into the crankcase. Gasoline vaporizes from warm oil, but diesel needs to get hot before it boils away.