Well, yeah, of course SH Down-B is a viable option, but realistically, it wouldn't work everytime you needed it, for every laser that Falco shoots, due to how fast he does it, unless you just SH Down-B and leave it there. But even then, that risks a punish for Falco to get on you.
Falco also doesn't have a hard time gimping Pit, but he does get gimped pretty darn easily by Pit, that's the only thing I think Pit has the advantage of in this MU, is just being able to gimp quickly. It just seems like, Pit should wait for Falco to mess up and then take advantage of it to win, but in a fair neutral game, I do definitely say Falco's favor, at least 60-40.