Hi troopscott,
Welcome to FlyerTalk!

Unfortunately, you have missed the point of the Mileage Run forum.
Please read this thread to understand that the forum is for particular fares only:

Sticky: Welcome to the Mileage Run Forum - Important information how the MR forums work

Your question has nothing to do with Mileage Run (fare) Deals.
I have moved it to TravelBuzz! because the question is about the busiest airports, which is a much-asked question on the forum.

Please have a look around TravelBuzz for examples of this kind of question.

If you want to get an answer to your question, I think you should detail which airline you fly and your travel patterns, because the airline, airport, time of day and day of the week would greatly affect the answer to which is the 'best' airport, aside from the possibilities of the airports acting as major hubs.

These days, the conventional answer may no longer apply!

Cheers,
BiziBB
Moderator, Mileage Run forums