It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

which is better ? GOG OR STEAM version ?
They're the same.

If you buy on GOG you directly support the developers as all the money goes to CD Projekt.
On top of that there's no DRM involved here. The Galaxy client is completely optional. You don't need it to download or play the games.
GOG is always better than steam. GOG = No drm. steam = drm.
Gog, DRM free and all of the money goes to the developer of the game.