A couple of observations-I operated pet grooming trailers for 3 years. These trailers relied upon a propane-fueled onan generator. Lots of breakdowns. Replacement vehicles are diesel vans which have a bank of 12v batteries, a 90 amp alternator, and a 3KW inverter. Lots fewer breakdowns. Easier to get service on the parts that break, cuz the alternators and inverters are relatively easy, tho costly, to replace. This is a configuration used in FEMA and Red Cross disaster response vehicles.

The argument in fuel choice seems to me to hinge on fuel storage and availability. Locally, the electric power fails pretty often (village is suing power company for this lack of reliability) and natural gas has not failed so far. Large volume, long term storage of diesel or gasoline presents some problems in safety and loss of fuel quality over time. We chose a 5KW gas fueled permanent installation for back up power, and have good luck with it for 6 years; but, as raspy points out, the engine is still basically a lawn mower motor, and is not as reliable as a truck engine would be.