The big selling point of Unification is the new factions, but realistically you’ll get a lot of mileage out of improved AI, as well as big updates in the campaign and new win conditions usable in its missions.
The unification mod adds new art and units for the nine base game factions, as well as 17 new factions. If you like Warhammer 40,000, have I got the mod for you: Unification Mod for Dawn of War: Soulstorm is a sprawling remaster, bugfix, faction-adder, and game mode adder that works for both the Steam and (to my delight) Actual Physical DVD versions of Dawn of War: Soulstorm.
