Songs: ERIKA - Her songs were far better than YUI's.
Acting: ERIKA - Her acting is obviously far better than YUI also. YUI was just bad.
Vocals: ERIKA - I love her voice. I can't stand YUI.
Musical talent: YUI - She knows how to play guitar while ERIKA doesn't.
Personalities: ??? - No opinion about that. I don't know much about YUI at all and Erika Sawajiri can be quite something, haha.
OVERALL: ERIKA
Plus, Taiyou no Uta the drama totally owns Taiyou no Uta the movie.