I've never really liked either of them, but... I can't believe I'm saying this, but I think I would rather have Fantasia win. While I earlier found Fantasia the most annoying of the 12 finalists, she hasn't gotten any more annoying than she was in the beginning.
Diana has also been annoying since the start, but every week she just gets worse and worse. Her Disney shtick just gets on my nerves more and more every week.
I was tempted to stop watching after George got booted, because he was really the only interesting character that was left. After Latoya (IMO the best singer in the whole competition) got booted, I did stop watching. So I guess the real answer is that I don't care who wins, I won't buy their album and I will not listen to their music on the radio. 😉