"Supper's Ready", definitely. Apocalypse In 9/8 =
Had it been "Supper's Ready" vs. "The Gates Of Delirium", I would have got with the latter due to the insane middle battle section and the beauty of the closing section "Soon". "Gates" always seemed a bit more comparable to "Supper's Ready" in my mind, being that they are similar length (TGOD clocks in at 21:56 compared to CTTE at 18:43), they have similar subject matter (battles and war involved), and have memorable closing sections.
However, "Close To The Edge" is more defined as being Yes' definitive epic and while I love it, I just find "The Gates Of Delirium" a bit more interesting, but since this is not the case here, the clear winner is "Supper's Ready".
-Marc.