Dark Pit vs. Pit (What makes them different?)

[PixelChaos]

So I've been wanting to main Pit/ Pitoo for a while now, but have trouble noticing the differences between the two.
I've noticed many early tier lists put Pit and Pitto generally in the same tier with only a few points difference, but Pittoo always comes out on top. I am a competitive noob, so besides the difference in arrows and asthetic value of their side-b, what separates the two?

 

[SamuraiPanda]

You can ask this on the character specific boards or one of the general question FAQs.