Why it took nearly 8 minutes for the judges to decide between Sami and Kitty I don't know. For a moment I thought that Louis was going to say he'd send Kitty home just to leave it at deadlock and then the act with the lowest votes would have been sent home.
My guess is that he genuinely does think Kitty has a better chance of lasting longer and that he also sees how poorly she has identified with the voting audience to date. So there was a big risk that she might have been the bottom in vote numbers and he'd have lost her.
Incidentally, Kitty did produce an excellent performance of On The Edge.
So bye Sami. You won't be missed much.