The orchestral one should have a live choir, unless you happened to get an instrumental version of One-Winged Angel orchestral, which is a secret song in FF7 Reunion album. There's 4 versions with the choir:

1) The one in FFVII OST
2) The one in FFVII Reunion
3) The one in FF Concert 2002 (quite similar to Reunion version, though a bit more spooky sounding)
4) The one in Kingdom Hearts (Final Mix album)

You can either buy FF7 OST or Reunion or try searching for one of those OWA versions with file sharing programs or from web sites. I think EoFF also had One-Winged Angel available for download somewhere.