Sure I'll contribute my 2 cents in.
I firmly believe this should be a -2 in Sonics favor for several reasons.
1) Pit has no realiable way to safely approach Sonics spin dash. So you wind up shielding all day until the spind dash eventually stops.
2) Sonic can easily abuse the large stages, like FD and Duck Hunt to time players out. Whenever Pit tries to over commit or even takes a small risk, Pit will get punished into oblivion.
3) The springer can really hinder Pits recovery. Sonic can easily dive down deep for a fair stage spike. Also, Sonic could use a well spaced down angled fsmash to hit Pit in the face, making it even harder for Pit to land.
4) Pit will have a difficult time landing safely from most of Sonics attacks, thanks his his fast running speed. Using the guardian orbitars will not help you out very much as Sonic could continue to juggle you around once Pit drops the orbitars. The best way to safely land is either grabbing the ledge (as if your fighting Rosalina), or find a safe area to land without doing anything. Fortunaetly, Pit can A-Land with his dair to any moves, like jab or grab to quickly respond to Sonics dash grab or dash attack.
5) If you use a move, like any smash attacks or side b that could potentially leave you wide open, Sonic can punish you with a grab, running usmash, dash attack, etc. Even if you whiffed a dash attack or grab, you will still get punished severely, so you would have to play extra cautious. The interesting part about Soncis Fsmash is he will pull back, causing Pit to whiff the dash grab/dash attack and smack him in the face with a "Pow!".
6) Pit is very limited in terms of getting back on stage because Sonics usmash can cover getup attacks, normal getups, and jump. From my experience against the better Sonic players, jump airdodge at the same time to avoid Sonics charged usmash.
7) A lot of Sonics attacks seem to barely have any cool down, so try not to get baited by his attacks.
Pits advantage
1) Once you grab Sonic, you can juggle him around for days until he can land safely. Even if Sonic were to use the springer as a "get out of jail" free card, his only options are to land with dair or grabbing the ledge.
2) Sonic has no real way to combat Pits arrows offstage, except for fair. If you land 2-3 arrows in a row on Sonic offstage, his only option is to use the springer. A well timed fsmash can seal the stock while Sonic is landing from the springer.
On stage though, his arrows are useless, unless you try to dash away with a turn around full hop arrow. Although I wouldn't recommend doing it too much as you lose stage control, thanks to Sonics fast dash speed.
3) Thanks to Pit's disjointed hitboxes, there are some ways to counter Sonics spindash, but you need to time it properly to stop it. Moves like jab, pivot ftilt, shorthop nair, fair and dair will be very useful in this matchup.
4) We should be blessed that Nintendo nerfed Sonics bthrow, so we don't need to worry too much about Sonic grabbing us. It is still Sonics best kill throw, but we can DI the bthrow and survive for a really long time if you play the matchup safely.
What not to do against Sonic
-Falling aerials are what Sonic players strive for.
-Throwing out usmashes and get his in the face with a bair. If Sonic airdodges Pit's usmash, Sonic can safely hit him with a bair.
-Using arrows on stage
-Using guardian orbitars to land
-Don't get hasty with your dash attacks, grabs, smash atttacks, etc.
-Normal getups are definitely a no-no in this matchup. Same goes for getup attacks and jump above stage.
-Take him to Duck Hunt, or Final Destination
-When you see Sonic tossing out empty hit boxes, don't get baited, unless your confident that Pit can safely land a hit.
The matchup is usually defined on the players play style. An agressive Sonic will lose to a patient Pit. However, a patient Sonic can pretty much beat Pit, unless you manage to outplay Sonic and figure out their movement patterns. Every players playstyle is different. In general, I would say Sonic can overwhelm Pit with no room to breathe as well as playing a good hit and run game.