I don't have as many titles on gog at the moment so Divinity: Original Sin Enhanced Edition since I just finished installing it.
But to choose from my steam collection Thief Gold

Lords of Magic Special Edition , absolute classic :)

Considering you have multiple copies I thought you would chose something else :)

I would definitely pick Primordia for myself.

eh im lazy
and a drm free installer is easier to grab then any of my disc versions ( i also play the game on my optical drive less laptop )

and finally i just want to have all the versions