The GOG release is optimized for modern Windows systems, solving many of the crashing and resolution issues found in original 1999 copies.
What's the difference between steam and GOG? : r/gamingsuggestions System Shock 2 Free Download (GOG)
The GOG version is highly compatible with the "SS2 Tool," which facilitates the installation of high-resolution texture packs and "Nightdive’s Enhanced Edition" features. Completion Time The GOG release is optimized for modern Windows