TomNuke: Why would you go back to Steam? If a game is available on both GOG and Steam you always buy on GOG.
If I buy something on GOG I basically "own" the game. Assuming I download the offline installers and take care of my personal backups (you're stupid if you're not backing up your offline-installers) no one can take that away from me.
That's not the case with a rental service like Steam. Valve has straight up said that Steam is a rental service. If something happened to Steam or Valve, well, you're entire library is more or less gone. If something happens to GOG, well, my games are fully useable and in my possession. I'm not dependant on some shitty App like Steam to install and retrieve the software I paid for.
GOG = Here's your purchased software. It's your's to keep forever, and even if something happens to us. Just make sure you don't lose it!
Steam = Here's access to your "lifetime" rental. If something happens to us though, you'll no longer have access to our service and therefor any of the software you thought you "owned" when buying from us.
But seriously, GOG is not going anywhere. The Summer sale will be starting soon (hopefully tomorrow) and you should always buy with confidence. Feel good knowing that if you buy something on GOG you're getting the best version of that game possible, because it's one that you have control over and actually "own".
No GOG = No buy.
Depends on the game and the version available. Some game have more DLC's, more features (often proprietary), and more support elsewhere - especially newer titles.
See threads like this, when GOG versions get 2nd class citizen treatment:
https://www.gog.com/forum/general/games_that_treat_gog_customers_as_second_class_citizens_v2/page1 For older titles - yeah, GOG's usually the better choice. Often, titles get fixes and/or things implemented out-the-box from GOG. Less muss and less fuss.
For newer titles - eh, depends on the support from the dev's and/or pub's on the said game.
About DRM-FREE - can't beat that, especially when it comes to Single-Player titles. GOG is where it's at, for that.
Though, there are some titles on Steam, that don't have DRM wrapped about the game's actual EXE itself - making it DRM-FREE once you download the files through the closed client-app (Steam). Just back those up elsewhere and whatever dependency files needed (i.e. PhysX drivers for some games; VC files; etc).
Problem is - Steam doesn't really often make that stuff public. We have to hunt on GOG Forums, Game Wiki's, Steam DRM Wiki's, and other things like that.
And sometimes, some games...it's just flat-out cheaper on Steam.
I ain't gonna live forever...and neither is Steam, Windows, etc etc. Gonna play what I can, while I can.