The smaller the bubbles the better. The micro-diffusers are expensive and a waste of money if you ask me. The Large Cylinder air stones are my favorite. But I mean... air is air.... Some argue plants require less oxygen than fish and fish only need a small waterfall/waterpump to supply all their oxygen. Other growers swear by air stones and others swear by strictly using water falls.
I run 2 commercial air pumps with all large cylinder air stones. One pump per system.
@ttystikk Has me convinced about dropping the air stones for a run.... We'll see
If you are lucky enough to have him pop in here and throw some advice around, he knows most of his shit.