Well, I saw someone comment my skills with Sonic, so if you think I'm good, Allied knows his ****.
I agree that it's either 50-50 or 55-45 Sonic. Those last two matches between Allied and I were kinda rushed, since we were asked to get off for tournament matches. Allied is a very good player no doubt, and I don't mean this personally, but I probably could've won that set, considering the first match was a 2 stock. Kirby isn't as hard as some think for Sonic :/
Since ROOOOY covered up the common Sonic misconceptions (thanks bro
) let me cover what Sonic WILL be doing (Allied did this very well, but I just want to post my thoughts without any direct quoting of anyone else, or correcting anyone else)
On the ground, Sonic will generally use ASC (aerial spin charge) to poke at Kirby's shield and get him in the air (ASC hits people up). I also find that RAR Bair works very well against Kirby. For those of you who don't know, Sonic's bair has a sourspot, and a giant hitbox. It covers his whole body, extends past the tip of his foot, and actually has a whole hitbox UNDERNEATH his leg, that's not even connected to his body >_> very, vey disjointed...don't underestimate.
From what I can tell, Kirby can't handle shield pressure very well from ASC and RAR Bair. Kirby's best bet is to try and grab Sonic, but even then, Kirby's follow ups don't generally work very well since Sonic can just spring away.
On the ground, I'd say it's an even matchup. Mostly since Kirby's grab range is so beast, and he has enough tools to make it harder for Sonic to get close, but even then Sonic has a great shield pressure game thanks to his ASC.
In the air, I think Sonic really excels. This matchup generally consists of Sonic getting Kirby in the air and abusing him. All of Kirby's aerials are outranged by Sonic's bair (except for maybe Kirby's bair) and Sonic's fair makes for an awesome aerial punisher. It comes out quicker than all of Kirby's aerials (I may be wrong on this, but I believe this is right) Sonic's uair is also MAD disjointed. It hits much farther than it appears to above him, and outranges almost any dair in the game (except for like...Link and G&W)
Kirby may have multiple jumps and his final cutter, but he generally moves too slowly in the air to handle Sonic. His UpB is also very prone to Bair stage spiking if not done smartly (this is pretty basic, but just a reminder). The only troublesome thing really to this matchup for Sonic is Bair, Grabgame, but most especially Kirby's ability to kill so early with Fsmash and Usmash. I honestly think Kirby's ability to kill so well keeps it from being a 60:40 matchup in Sonic's favor...
Kirby's fsmash is scary as ****, lol. Kirby's bair won't be killing in this matchup, cuz it'll probably be too stale from just trying to ward off Sonic. Kirby's hammer is suprisingly good, lol. Allied showed me that the hard way XD
So that's basically it. Kirby needs to get more grabs than Sonic, spam bair, and save his Fsmash or Usmash for a GUARANTEED kill. Sonic can live to surprisingly high percents. He's right above Mario in terms of weight, and his Fair + DownB momentum cancel is GREAT. Sonic's shouldn't be dieing till at least 140% (I'd say use Kirby's Fsmash/Usmash around 100-110%) Add that along with Sonic's amazing recovery in general, and you got yourself a tough matchup.
Inhale is a joke.
My final verdict is 55-45, Sonic. Any matchup where Sonic has near total control over the stage is a disadvantage.