Does the steam version have drm, out of curiosity? as itch does not do DRM. I would like to be able to play the game offline.
I have bought it on steam and it seems it runs without needing steam to launch, so my question is satisfied. I would have bought on itch but the original disillusion appears to only be on steam so i preferred to have them on the same platform. I do note that the original Disillusion does require steam to run.
Hard to say, steam games that can launch without steam (e.g. Disillusion ST, the Hylics series if you know that one), can launch from in their folder without turning the app on (or if it's on, without showing as 'running', but this isn't a guarantee that it won't work without steam on). Just have to try it without the app on to see