I've only played 6, 7, 8, 9, 10, and 13. So i checked those out.

7 and 8 are by far the strongest. But I went for 7, just because Sephiroth was more significant than Ultimecia. Plus 8's was used for Edea, who didn't even turn out bad.

9's is ok but nothing special. I don't like 13's, but it does improve when the choir comes in.

6 is far too dated sounding for me to appreciate, and 10's is unlistenable.