Is it better to have an avatar that is a picture of you, or one that is a symbol of some sort?

My avatars are me, except (maybe) for Captain America, which I use rarely.
I was thinking that maybe I should just go with a symbol or some sort of iconic image.
Just in case people respond negatively to the cult of personality that might arise around an avatar. I need all the help I can get.

What are your opinions. The real thing or a symbol or icon?