Yeah I feel like it comes down to whomever approaches the least in Marth Falcon.
Couple things I remember : Uthrow Utilt around 40%
Uthrow Fsmash without moving around 80%, even on no DI, albeit an uair before is better.
Dash dance a lot, keep it as tight as possible, Falcon has speed so you just want to deny him a small part of the stage and make sure he can't approach you there, while still moving of course, rather than running around trying to outrun him, which you won't be able to do.
When you get a hit in, focus as much as possible, you need to compensate for Falcon's combos, keep it going, techchase a lot, throw him out, be patient in edgeguards, as long as you throw him out again you're fine.
Don't hesitate to hold the ledge and go for reverse fair and regrab the ledge if they come from underneath. If they don't you can waveland on stage then dash off fair, or variations of these.