Agree with city names. Even people who know airport codes don't always think in those terms - and some cities have more than one airport.

A few years ago AA's JFK monitors showed departures in alphabetical order by city name. (Maybe they still do, but it's a while since I've looked.) At the time they had just begun service to Worcester, Mass. (since discontinued). Apparently the people who set up the monitors didn't know how to spell Worcester, so they used its ORH airport code. With departures spread out over eight screens or so, that made it really hard to find!