Yes, but Steam seems to have more games to offer (I am aware what GOG stands for). I just hate splitting my collection in half, you know? DRM or no DRM. GOG only has a few exclusive titles that I'd like to use. Ignoring mainstream stuff like Team Fortress 2, CS:GO, DotA 2 or Warframe.
STALKER Shadow of Chernobyl is 16$ on Steam, 18$ on GOG.
Oddly enough Clear Sky is 1$ cheaper on GOG
Call of Pripyat 2$ cheaper
Thief Gold is 7$ on Steam, 9$ on GOG
Yet System Shock 2 is 2$ cheaper on GOG
EDIT: f**k this, I guess there's no choice but to choose both.
Which one do you personally use?