It depends on the abilities of your 'shell'.
CO2 will go farther but requires a special charger and special shells. If you go to Madbull Airsoft's website (incompatible with Firefox), you can find which shells are compatible with and designed for CO2 as well as two filling devices.
Furthermore, CO2 shells are not allowed at Best of USA Marketing events.
Red gas is in kind of a limbo, like, sure, it will go into standard 'flon' shells but it will blow the seals.