I think Simon said it a while back, your show has to be memorable (hopefully because of good not bad). So, I am using that criteria to measure yesterday's performance.
For me, the last two performances, James Durbin is the best. Maybe it's because I love rock music and get it? But, I think James has a great vocal. I thought he can only scream, but yesterday's performance - Maybe I am amazed - shows that he can control his voice.
My vote for him ...
My other fav contestant is Thia ... (but yesterday's performance was okay only).