barjohn
I have tried both and find the 810 fidelity to be better than the 820. The 820 has better battery life and is slighlty smaller. I have not tested in an airport but have spent time driving with them. I like the 810.
As you can imagine I'm in a position to try whatever whenever and often do... the unit I haven't tried yet is the new Nokia and the NEW NEW SonyEricsson.... but you didn't ask about those!