Have the original Warrior Kings still in box, loved playing it but never finished it.
Was wondering what is different between the two games?

its basically the same game, but better

what's new?

-slightly better AI overall
-new AI personalities
-slightly better graphics, mostly textures, and tree sprites
-better skirmishes with diplomacy and extra settings
-some new units
-balanced unit stats, and little tweaks here and there

-different campaign, you have to conquer the map, province by province, and each time you are successful , you unlock new stuff, like AI for skirmish matches

Warrior Kings has extensive campaign.
Warrior Kings: Battle has some fixes but with no campaign.. just conquer the map style, I believe