I'm beta of WoR too... and I love M&B Warbands: as Untamo says, the detail of the single player campaign is really deep.
Anyway, if we're going to talk about feudal simulation, nothing beats "Crusader Kings II".
It's wonderful when you are old, without living male children and you search of a "good young lady" to spawn babies... then you find an available young princess and you're celebrating until you find out that she has gonorrhea.
Here I'm the Scottish Emperor, but started the game as Duke of Moray (YEAH!)