falcon's hitbox with uair is much smaller than ganons, and it doesn't extend as far behind him or below him.
if you want to edge guard with uair, it's better when used after a ledgehop, because it forces them to go above the stage. you can also moonwalk uair which has surprisingly long range. uair is a good edgeguard if you can't really guess where they're going sometimes, because of its range. utilt also covers the ledge pretty well because of knockback and decent priority (as long as it hits firefox, i'm fine even if i get hit also.)
however, much better edge guards are bair... or jumping all the way out and kneeing, or knee tap to knee/uair. just become deadly accurate and edgeguarding isn't really a problem. you'll find yourself outright killing people instead of needing to edgeguard them.