It would be if the owner remembered to treat their diesel supply with anti-gel during the winter.

The great part about propane is unless you have a leak it will be there when you need it. I don't know the freezing point of propane. I am sure it has one.

Starting a diesel or gasoline engine on propane is a challenge. The industrial units I have seen have one source or the other to start and switch over to propane after they are warmed up.

Also when such a unit is shut down someone has to remember to charge the fuel lines with the diesel or gas and flush the propane out of the fuel system. Otherwise they will be tough to start the next time.