The OP's RV is probably on the Ford E350 chassis.
91tiger .... if so, will/does it have an approximately 36 gallon fuel tank or a 55 gallon fuel tank?
If it's the 55 gallon tank then IMHO it's a no brainer - go with the gas (Onan?) generator.
With that setup you either get about a 500 mile travel range with no generator run time ... or a whole bunch of generator run time plus a goodly amount of travel range on top of that.
We love that setup in our 24 foot E450 Class C and as a bonus the Onan is even fairly quiet and vibration-free for pleasant long runs of the air conditioner when drycamping. I estimate that our built-in Onan generator consumes around 0.4 gallons of gasline per hour when running the 13.5K BTU air conditioner (... if the compressor portion of the air conditioner is cycling some, not running continuously).