Dtilt is very nice because it has those IASA frames stuff, and so i has little lag, good to spam against chars that stay a lot on ground, like marth dittos, peach, ICs, dashdancing *****es
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Ftilt has amazing hitbox and less lag than Fsmash, so you can do like...surprise attacks with it, like a Fwavedash -> Ftilt. Tipper has high knockback. Not good to spam with it cause you can get punished worst than with Dtilt.
Jabs are for them not to approach you, i find it like a secure way to stay defensively, you can still shuffle Nairs and Fairs and mix with jabs
On edgeguards:
jabing spacies fowardB is sex and safest way to get a kill.
Ftilt is nice at covering options, like when they are fire foxing/birding and there is still a chance that Fsmash isn't going to hit, you can Ftilt, and if they evade, go for Dtilt or jab or something fast
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i would say Ftilt is the less used, then jabs, and dtilt is so good beacuse it comes and goes very fast.
example vid xD
http://www.youtube.com/watch?v=EWmAnhv7594
in falco's 2nd stock i use Ftilt for edgeguard, but i got slopy and didn't get the kill D:.