Generally speaking gas is cheaper to run. It is also better for heating as it is not elemental, but direct flame. Though the way power companies fluctuate, that may not be correct in your area.
The choice of ovens varies from brick bottom to conveyor ovens which use a combination of gas flame heat and direct airjet to "quick cook" a pizza. I think it all depends on what you are looking to do with your pizzaria.
Pizza hutand others, I think , use only airbake ovens with conveyors. Alot of chains do this. you get an ability to mass cook pizza by putting the raw product in one end and the cooked comes out the other. These are good for making pizza that pretty much are uniform in looks and taste, and getting clients in and out effeciently in the shortest time possible.
The older style brick ovens mimic the traditional fire heated ovens that pizza was originally created with. They are slower, tempermental as they creat hot spots and cool spot in the brick. These are more for pizzarias who want the smoky atmosphere, with low lighting, and a longer wait time for the customers to enjoy a more personal touch type of pizza. It does as I said, generally take a bit more time to cook a pizza as the heat is not directed onto the pizza, but more radiates.
My personal taste is for the brick style. I think you get more flavor incorporated by the "oven" quality versus the chain/belt conveyor being injected with heat.That is merely an opinion of mine as I am sure there are some who prefer the flavor of the conveyored pizza. While this does not directly answer your questions, I hope this helps a little.