Sean,
This might seem snarky, but it is not. This type of aerator uses a propeller, not a fan to lift some amount of water and toss it through the air to add O2.
Surface aeration is used to add O2 to the water. While it does pull some lower water up, its main job is to add O2. Fountains, are the least efficient. And bottom aeration is used primarily for mixing the water column (braking a thermal-cline) and off-gassing dead bottom water.
So the surface aerator was used to add O2.
Bottom aeration should have the least evaporation, but it does a different job. None of them add much heat to anything as the volume of water will be easily able to handle the added minimal heat. Now if you were asking which will mix the water and have single temperature body of water, that would be the bottom diffused systems.
And fountains are pretty. While they do mix a little and do add O2, they are the least efficient/ most expensive way to add O2.
So remember, they all do different job for your ponds. Use the system that will match your goals.
