I think Falco vs Sheik is a really interesting match up because of a couple things, first of all lasers vs needles both control the stage in very similar ways but from entirely different angles, so the projectile game has a lot of depth in this match up because both characters are controlling each others approach pathways.
If Falco hits with a shine or a drill at a low percent then sheik is gonna go off the stage before she has a chance to recover and a good falco can keep edge pressure going until a stock loss.
If Sheik hits Falco with anything short of a fair at a semi low percent it leads into the above, and even then if she doesn't space perfectly it leads into the above. If Sheik grabs Falco then Falco is off the edge, and his stock is over. But Falco is a very difficult character to grab as well. Both characters have to space so well that its just ridiculous.
But yeah I'd say its a little in Falco's favor on big levels, in Sheik's on small levels, I couldn't imagine beating a good Falco on FD because I couldn't control the match with needle at all and I would be at a terrible disadvantage the entire game through forced approaches, well until you throw powershielding into the mix, then you have a lot of grab opportunities.