For me, although I no longer tow an RV (it was a 39' FW when I last RV'd), I have 2 diesel vehicles and 1 gasser that are used for towing. For most of the towing, I use the F250 so that there is no problem when I'm pulling the boat or the sno go trailer and push down on the pedal, something happens other than a gas engine wrapping up to 5k+rpms. I know it's more semantics than physics, but I'm just more comfortable towing loads that get up into the capacity of the TV if it's diesel. Some concept on the "big" truck: when the equipment trailer needs to be moved, and I hook up to the F550, I know I won't set any speed or mileage records, but it will go.
The Sequoia hauls the jet ski, the kayaks, and the log splitter just fine.
...and as an added thought, it wasn't that long ago (although maybe 8 - 12 months) that diesel was priced lower than gas and fuel cost was cheaper in the F250 for a non-towing road trip than in the Sequoia.