Thanks for the analysis turtle.
I own a diesel so I get it, but in order to arrive a true net, you must factor that the diesel engine costs about $10k more.
I don't much care about mileage. If I was concerned about mileage while RV'ing I would have bought a Sprinter. That said, the 6.7l turbo diesel mated to the 10 speed transmission gets surprisingly good mileage even while towing. I also keep trucks forever and diesels just last longer than gas. They are also more efficient at producing power - mileage alone tells you that. But the new gas engines are amazingly powerful and efficient compared to just a few years ago.
There are pros and cons to each. In a modern truck either will do the job. Not sure why this becomes such a heated debate and folks have to justify why they own what they own. Choose what works for you.