I recommend airport, largely because it's more convenient to me, and likely many others as well. Also strikes me as a little nicer part of town, generally speaking.
Med Center has market saturation, with the majority of incalls being hosted there. Also, the average hobbyist at any given point in the city is likely to be closer to the airport, with its central location. Makes you more accessible to travelers as well.
Just my two cents. But whenever I see "airport" in an ad, that grabs my attention more than "medical center."