I agree with jludwig.
I am NOT an aeration expert, but have read lots of posts by our experts, so I will give it a stab.
To noobie me, it seemed that an efficient centrifugal pump would move a LOT more water than the air pump flow through a bottom diffusion aerator, and therefore be more efficient for oxygenating the pond.
However, there is one step in the process that is not immediately intuitive. That is the buoyancy effect of that rising column of air bubbles! If the water pump had to LIFT water up by 16 feet, then the electrical costs would go up dramatically. Instead, the air column lifts massive amounts of water from the depths of the pond and delivers it to the surface - without any "mechanical" inputs by the system components.
Part of the subsequent oxygenation comes from pond water in contact with the tiny bubbles, but I believe most of the oxygenation comes from the water being delivered to the air/water interface at the surface of the pond where it can be directly oxygenated, or mixed with other well-oxygenated water.
Literally every commercial operation I have seen uses air diffusers for oxygenation, so I expect they are all getting the most oxygen in the water per dollar spent.
[Experts, please feel free to correct or expand on my explanation in this post.]
