My favorite OWA version is the one played live at Distant Worlds in Stockholm on December 4th, 2007:
YouTube - Distant Worlds Stockholm 4/12/2007 FFVII: One winged angel

I think it's much more intense and "packs more punch" than other versions. It also sounds like they're playing it a bit faster than usual. The one on the Distant Worlds CD isn't as good - it's much "softer".