With the max flo (which comes stock on a shocker), it won't go liquid or fluctuate so you don't really have to worry about that. You get more shots per fill with CO2, so if you go through alot of paint and don't want to burden yourself with a 114 air tank, it can be a reasonable alternative. My personal preference is air because it is cleaner, more consistent, and unaffected by temperature fluctuations, but that's just me.