Yeah... So given how often I've heard both of these, I did my usual "play them back to back while doing other stuff and see which one you remember more of" test. And listening to One Winged Angel... there's this anticipation throughout the entire thing that just isn't there for the FFVII Main Theme. I spend most of it like this: "yey! it's the build up to 1:10, whee! now we're at 2:15, nice! some downtime at 3:00, oh! let's rock out to 3:22!, now we get to start all over again!".
The FFVII Main Theme is a great theme, but it feels a lot more passive then One Winged Angel. It's one of those themes that sounds great when I hear it, and is obviously a well crafted theme, but it doesn't really grab me. One Winged Angel grabs me. A lot.
I'd have to disagree with Obs. OWA is fantastic but the Main Theme just makes my heart swell in a way that OWA doesn't, particularly when the percussion kicks in after a slow build up and it all comes to a crashing climax before dying down again... God. My heart. My heart.
I tried really hard to find a .gif of Cloud removing the Shinra helmet during that denouement. My hearrrrt
With the main theme, I actually find it tough to choose between listening to the original soundtrack and and orchestrated version. Whereas with OWA, it's orchestra or bust, and since we're voting for the game track, this was a cinch.