Though I love Northern Shaolin Kung Fu (fire bending), I'd have to say that my heart is with Tai Chi (water bending). It combines the best elements of all forms of bending offense, defense, and control, and it even has the power to heal. I'm a pretty laid back kind of guy, and I've always enjoyed the "flow" of things. From the way that gears connect in a complex machine, to the excellent choreography in a high-level fight sequence in some of my favorite Kung-Fu films, flow has always been a major fascination to me. And one of the founding principals of martial arts is to be like water: formless, yet can take on any form; powerful, yet can let any object of any shape pass through it. Water is king.
As for advanced airbending, Sound manipulation can be a useful and very dangerous thing. Being able to nullify the vibrations around a room could make it sound-proof (a.k.a. secret meetings ANYWHERE!!!), increasing one's hearing and or communication skills (instant loud-speaker!) or being able to destroy things by vibrating at a high-enough frequency. Plus, if controlled correctly, it could easily knock someone unconscious, making it even more aligned with the air bender's creed of non-killing. And since sound is generated by the vibrations in air, I'd say it suits air bending perfectly.