I hope you all love numbers! Since no one else bothered, I come from the Lucina forum bearing data on both Pit and Dark Pit.
@
Neo Zero
This might be something to have in the OP of the thread since the Pits differences seem to be a common question.
Foreword: So some characters in this game have decimals in their damage numbers; Pit and Dark Pit are two such characters. This means that there's a hidden damage value adding up when you do damage (training mode will only register whole numbers in the data feed-back it gives so it's easy to miss) but the most important thing is that these decimals affect Knock Back (we think at least) meaning Pit and Dark Pit get a little extra distance on-hit than characters doing the same whole numbers of damage.
One last thing that's important to clear up beforehand, Dark Pit isn't any slower or faster than Pit. Their animations are all the same.
Anyway, here are
Pit and Dark Pit's Damage Outputs:
Jab 1 - 2%, 2%, 5% (Pit) - 2%, 2%, 5% (Dark Pit)
Jab 2 (Rapid) - 2%, 2%, 1%~~~, 2% (Pit) - 2%, 2%, 1%~~~, 2% (Dark Pit)
Forward Tilt - 7% (Pit) - 7% (Dark Pit)
Down Tilt - 6% (Pit) - 6% (Dark Pit)
Up Tilt - 2%, 3%, 5% (Pit) - 2%, 3%, 5% (Dark Pit)
Forward Smash - 5.1556%, 10.1556% (Pit) - 5.1556%, 10.1556% (Dark Pit)
Fully Charged Forward Smash - 7%, 14% (Pit) - 7%, 14% (Dark Pit)
Down Smash - 12.3334% (Pit) - 12.3334% (Dark Pit)
Fully Charged Down Smash - 16.5% (Pit) - 16.5% (Dark Pit)
Up Smash - 2%, 3%, 8.334% (Pit) - 2%, 3%, 8.334% (Dark Pit)
Fully Charged Up Smash - 2%, 4%, 11% (Pit) - 2%, 4%, 11% (Dark Pit)
Neutral Air - 0.6% x7 Hits, 4% (8% Total) (Pit) - 0.6% x7 Hits, 4% (8% Total) (Dark Pit)
Forward Air - 1.5%, 1.5%, 4% (Pit) - 1.5%, 1.5%, 4% (Dark Pit)
Back Air - 12% (Pit) - 12% (Dark Pit)
Down Air - 10% (Pit) - 10% (Dark Pit)
Up Air - 2%, 2%, 2%, 2%, 2% (Pit) - 2%, 2%, 2%, 2%, 2% (Dark Pit)
Neutral Special (Arrows) - 3.334% (Uncharged), 8.5% (Fully Charged) (Pit) - 3.8% (Uncharged), 10.5% (Fully Charged) (Dark Pit)
Side Special (Arms) - 11% (Pit) - 11.5% (Dark Pit)
Grab / Pummel: - 2% (Pit) - 2% (Dark Pit)
Forward Throw - 6%, 4% (Pit) - 6%, 4% (Dark Pit)
Back Throw - 8% (Pit) - 8% (Dark Pit)
Down Throw - 2%, 4% (Pit) - 2%, 4% (Dark Pit)
Up Throw - 4%, 7% (Pit) - 4%, 7% (Dark Pit)
While I can't speak for Knock-Back angles, (I know their Side-B have different angles) Dark Pit is truly a carbon copy of Pit bar their Special Attacks having slightly different damage outputs and arrow control.
On the bright side, if you know how to use Dark Pit, you know how to use Pit just as well.