I know I'm a bit late here, but I figured it couldn't hurt. I use those Pocket Vortex footballs and Madbull Stingers in my AG-36, and I can get some pretty good distance from them. On a hot day, I've launched them farther than my AEG could shoot with propane (about the same as green gas). However, when it's cold out, propane can be a bit unpredictable and unreliable; I'm pretty sure C02 would be a lot more stable at lower temperatures, though.
And as far as practicality goes, I've found them useful almost every time I use my G-36. It can really help at Fightertown sometimes.