Warzone 2100 Legacy combines the underlying game enhancements of Warzone 2100 3.1 with the excellent game experience, technology tree, targeting, and balance of the long loved Warzone 2100 2.3, and includes a wide variety of additional enhancements, such as well implemented spectator support, an enhanced map and AI selector, IRC-style "/me" messages, many additional stock maps, loads of bugfixes including netcode of superior stability compared to any other version of Warzone 2100, and much more.
All Legacy is Warzone 2100, but not all Warzone 2100 is Warzone 2100 Legacy.