The operating costs are different for each and it depends on the price and type of power sources you have available. For me, if electric costs X amount, LP gas is about (0.7)X and natural gas is about (0.65)X to operate.
Find out the costs per kilowatt hour (kWh) for each power source in your area and you can easily see which is most efficient for you.
Be careful about buying the correct frequency for electrical controls, fans and conveyor motors. 60Hz controls from US ovens should not be used in 50Hz systems like most of the world uses. 50Hz components are fine in 60 Hz systems, though.