Hey there
I asked the same question once because of all the talk about 2.0001 or whatever in the forums. Back then, the answer was that the Steam version is the official version. The newer version is still an unofficial beta for testing it. To get it, ... I don't know, I dont want it right now^^
Also, if there will be an official updated version, then it will also be updated through steam.
Right now, there isn't an update for each and every little beta change on steam because steam charges Arcane Games each time they bring an update, so it would be stupid to pay for each update right now. I heard there had been a lot of them, they're balancing it all out right now.
Hope I could help you.
Everything correct x4000 ? ^^
EDIT: oops... while writing, there have been answers posted^^