Highly compressed files require a lot of CPU power to unpack. The "best" version strikes a balance; you don't want to save 2 hours of downloading only to spend 4 hours installing.
The clunky mechanics of the original are gone. You get the refined weapon handling and stealth takedowns that made the sequel famous. metro 2033 redux highly compressed best
Redux runs on the Metro: Last Light engine. This means better lighting, advanced physics, and more fluid character animations. Highly compressed files require a lot of CPU power to unpack
Removing optional files like extra languages or 4K credits videos. metro 2033 redux highly compressed best
Recoding heavy textures into more efficient formats that unpack during the installation process. Finding the "Best" Version: What to Look For