All share the same hassles to some extent or another. They have to be run, UNDER LOAD, an hour+ per month. They need the oil changed. They need clean fuel; #2 Diesel tends to grow weird bugs that clog the filters. The propane and natural gas can feed modified gasoline piston engines and turbines. Some Diesels run on a fix of #2 and gases. [The ultimate example -- a sewage plant will recover sewer gas and use it w/Diesel. If your userbase is full of BS; or your tie curls and your boss has 2 horns, you might go this route...] Natural gas has advantages of no storage hassles; propane does not go stale.
In earthquake country, natural gas is as prone to interruption as any other utility. The utility companies actually have shut off valves in the lines which shut off gas mains when seismic activity over a certain level is detected. Being as how gas lines themselves are prone to shearing fractures in the seismic event itself, natural gas doesn't buy you much as a backup fuel. Unless, you maintain your own tank, which takes you back to most of the problems noted above. Regards, Bill McCauley