This patch is designed for people who would like to have modern quality of models, textures and sounds for NPCs and Weapons. I strongly recommend it as it makes the game prettier and it feels a bit more in tune with modern times.
Vanilla Replay Addon is a mod/addon for Vanilla Stalker: Shadow of Chernobyl that aims to keep the original atmosphere yet implement some Quality of Life improvements, visual and sound enhancements, gameplay enhancements, some realism and engine stability.