Well...it depends on what you're looking for in a live concert. Are you more interested in a big and entertaining show or do you care more about the voice of the artist on stage?
I voted for
alan, because her voice is just AWESOME live! It's true that she is not an entertainer like Ayu, Namie and Kumi, but for me the voice is most important and that's why I picked alan.
But I love
Onitsuka Chihiro as much as I love alan, because her voice is just as great!!