do i get anything extra if i buy it on steam?
I'm pretty sure they focus on Patreon and Steam now. Seeing how the last update here is more than a year ago, you should get a bunch of new content there.
It's a good game and the development is pretty steady, even when there is trouble (e.g. health issues) the updates keep coming. So yeah, if you wanna invest in a game, this is not a bad bet.