quite a lot actually, the problem with the M&B version is that as was said, it crashes quite a lot, when compy took it over he tried to get it as stable as he could but the code is a bit of an unorganised mess
Most of the features you find in the original are being 're-imagined' for SoD:W, hopefully in ways that will be more stable, also there is a whole lot planned that isn't in the original.
As for what is in the original:
Edicts: When you setup your own kingdom, there are a lot of choices that you can make about how your kingdom runs, some that supprt villages over towns and vice versa, some that support peasants or nobles or clergy, all with their own plus and minus, plus a lot of other edicts like holy war and things.
Mercenaries: You have Mercenary camps all over the map in SoD, these units are also in SoD:W, but the full merc system has not been adapted yet.
Troop Upgrades: In SoD you cannot upgrade troops, unless a town has the right culture and buildings for the particular level up (this makes getting more troops a right pain early on

)
Invasion: this is obviously the big bit, where the imperial legion descend upon calradia to lay waste to it, unless ye the great hero can thwarteth them!
There is probably a lot more that I have forgotten...