My vote is for Wesmod. The mod is awesome, trying to create some challenge that is not present in vanilla MTW. Wesmod didn't allow the AI to create entire armies of peasants and Urban militia but instead you will fight average to elite armies and Crusades are something nasty to deal with, AI ships are fulling the map and can destroy your entire fleet in 2 turns. The mod really takes you into another dimension, it adds a lot of challenge. Playing hard in Wesmod is better than playing expert in vanilla MTW.

There are some mistakes like Almughavars bonuses in France, VG (Paranamoi) vastly decreased in armour, attack and defence or Mamluk cavalry as bodyguards in Early period but not in high... but you can correct it easily.