I just buy where a game I want is on the lowest sale at the moment, but still check if a game is properly updated on gog first, since some games haven't been updated in a long time on gog.
Tho I try and mostly focus on old games not on steam anymore or indie titles are are updated on parity with the windows release, otherwise I prefer steam, also cause I own a legion go with bazzite installed so it's easier to play games like that.