Well, let me start off with saying that you can only bend side elements if you can bend the main element. You can only lightningbend if you are a firebender (or the Avatar), you can only metalbend if you are an earthbender (or the Avatar) and you can only bloodbend if you are a waterbender (or the Avatar, you get my point)... So. Yeah. =w= You can't just bend a side element as to do so would require the basics of the main one.
Anyway! My sassiness aside, I would love to be an earthbender. c: My personality is also that of an earthbender. However, to bend air would also be awesome.
You wouldn't really be able to chose, but you can get a close guess based on your personality. For instance, these are not the only things linked to each element, but some basic ones.
Water - Change
Earth - Stubborn
Fire - Passion
Air - Peaceful
So I would most likely be an earth bender, I'm very stubborn. 3nodding
Water includes bloodbending, which is basically controlling people against their will.. and like in the show theres water in almost everything, including the air around us and plants.
So for me, it would be water, without a question.