Steam current version: 2.1
Itch.io current version: 2.1d
There is no leaderboard access or achievements in the itch.io version of the game and references to them have also been changed. With no current plans to bring them to this version. So if that is something you would want. I recommend you purchase the game on steam.
As of writing, the cosplay pack is not available on steam, only itch.io.
Control System - There is no current native support for controllers, However, using steams inbuilt functionality, it is possible to use controllers on the steam version of the game.