Looks like a good article.

It is recommended that you pull water from the surface because it does have most of the oxygen. Maintaining a thin, oxygen-rich layer is easier in an emergency situation than aerating the whole lake. Pulling anoxic water from the bottom of the pond may actually make things worse.

Now, if you're aerating for the long term, and you don't have a problem, pulling water from the bottom of your lake makes good sense.