co2 can be reused, or it would cost rental sites **** loadsair is just better for the eletric guns and air is better money over time as 1 air bottle can be filled over and over for up to 20 years but you will need to test the bottles every 3 or 5 years. Co2 runs out and you generally need to buy a new co2 tank worth bought £20 after everytime you go (depending on how many balls you shoot)
hope that helps