Jabbo,
First off, thanks for your service and I am glad things are working out for you.
I think with the inlets under the flame the air is fueling the fire and creating more heat. The air from the inlets above it does not get used completely as fuel, but still allows for the draft so you don't get stale bitter smoke. I think plenty of both is the best set up. If you build them to seal off pretty good, then you can have better control of your heat, as well as smoke in the cook chamber.
Just so I don't look too stupid, this is just redneck hypothesis. No scientific evidence has been collected by me to prove this other than playing with a few smokers.