Natural gas is measured in price per cubic foot, while liquid propane is calculated in price per gallon. Propane needs to be refuelled every time the level reduces. You can store it in a tank in the garage. Also, propane is multi-purpose as it can be used in a variety of electronics. It is also clean energy, so it has a very low carbon footprint. If you use propane for stove, furnace, and grill, stick to the fuel because changing fuels can be an expensive affair.
Natural gas is a lot of cheaper and is also eco-friendly. Also, it is delivered at your doorsteps when you make a call. Maintenance of generator that is run on natural gas is low cost. Longer you use the generator, less and less will be the consumption.