Hmm tough choice, I like both Air and Water myself. However, I would have to go with Air. Not only is it in junction with my Zodiac sign, but I love a lot of the stuff it can do and theorized as doing.
Flight: I always wanted the ability to fly, especially since I have a fear of heights it would help with that.
Changing air pressure: Not only could you effect someone's ability to breathe, you could also pressure cook someone or freeze them.
Manipulating air consistency: You could effectively create a charge to do lightning manipulation, create explosive gas (or I can do that if you give me curry

), or create moisture. (water + lightning).
Also the added bonus of being able to really screw with other elements: Fire (remove oxygen to kill flame or increase it), Earth (air pressure to create dust storms that could shred someone or
lift the ground beneath someone's feet then make it blow away), and Water (removing the oxygen from water, effecting the consistancy of water, etc...)
In terms of the Force, I like the potential for both Lightside and Darkside that Air bending is capable of...especially the destructive purposes.

It's good to be evil sometimes. Plus could you imagine
sapping all the Oxygen from someone's blood. Mwahahahahaha!