GOG has the structure right. Pay once, no DRM, download forever, no forced updates that requires an internet connection, no region locking, no currency scamming and most importantly: customer to company to customer trust. In other words, none of the shitty fucking bullshit Steam makes the unwashed masses endure.
Considering that one day GOG will have the same library as Steam, there is just no way as a human consumer of media to "prefer" Steam. Seriously, to hell with Steam.