Darkauraking: What would be the key differences between GOG and steam?
Steam is made by a company with more industry clout and technical skill.
Steam is made by guys who have a very corporate background.
Steam works well most of the time but when it doesn't, man it doesn't. whether that was a game not working for you because some publisher just barfed it onto the platform or running into the steam support wall, there were steam horror stories peppering the beautiful landscape.
Steam supports DRM (optional, but it makes it so easy for developers that most do enable. and all major publishers enable) and gog takes a vicious anti-DRM stance first and foremost.
gog is a nicer community in some ways.
gog have time and again demonstrated goodwill on a scale that perhaps surpasses even Valve with Steam.
gog generally costs more.
gog generally more likely can resolve all problems you might have with the service via refund or help from support.
gog is not as social a platform as Steam but this is in flux.
Steam has newer releases.
I don't really think of gog and Steam as "A or B" so much as "this and this".