If the same game is available and on sale on GOG and Steam, on which platform you rather buy it?
I've had this question looking at the Quake con sale, and Call of Cthulhu Dark Corners of the Earth is for sale on both platforms. I ended up buying it on GOG. What is your opinion?
GOG. DRM-free support needs all the help it can get. I have nothing but respect for Steam, so it's my secondary choice. The only exception is if it's a game that's been out for a while and there's been discrepancies between GOG and Steam support (or a dev/publisher with a history of said issues), in which case I'll go with the one that's better supported.