I personally do not recommend submersible pumps becausethey are cooled by the water so therefore heat the way ter to much. That and most people buy cheap submersible which have poor efficincies so they definiteely heat the water. Most air cooled pumps are pumps made for salt water aquairiums (or should be) and are therefore air cooled and magnetic drive so they contribute to very litle increase in reservoir water temps. Putting a venturi on their inlet means the pump chops up the air into very liite bubbles which means large suface area per air volume and long water contact time. Plus the circulay tive effect of the pumped water keeps the roots in motions so that all the roots are exposed to more high DO water rtaher than just the outter layer ogf the roots mass. Air pumps just do not put out a lot of volume at any water head. Air blowers are too noisy as they have an irritating pitch (whine) to their noise output. Lime wood/ bass wood have smaller bubble output but limited volume with small economical air pumps. Hardwood airstones such as oak have very small bubbles but require higher air pressures. About the best choice is a needle wheel pump but they require more maintenance (needle wheel replacments) than an air cooled pump with a venturi. An economical air pumpsis just too dismal in its air pressure and air volume output when pumping at pressures needed with wood airstones out put. If you spend much money then you might as well justs skip the air pump.
All in all you still need to consider only a DWC really benefits by airstones over a small pump as they have small air/water interfaces due to all the roots. Any reservoir with a large open air/water interface is more efficient kept at a high DO by just using a small aquairium power head pointed at the water surface. More air enters the water at the ar ir interface than through air bubbles unless you have extreme amounts of air volume IE a blower.