I have the stats for both of them. The Armoured Swordsmen lack any advantage over the Morgannwg Spearmen except for being just abit cheaper and having nearly the same upkeep(5 less). The Armoured Swordsmen have same attack, 2 less charge, 2 less defense skill, same morale, and less men(15 less on normal, and 30 less on large).
In the Kingdoms Expansion, the armour value of most units was nerfed while the sheild value was buffed. The defense skill of sword/axe/mace and sheild infantry was nerfed, while the defense skill of spearmen was buffed. Cavalry was also nerfed statwise aswell, possibly meaning that the spearmen buff was another way to nerf cav as before kingdoms spearmen couldn't hold well against mid-high tier cavalry. Regardless, the result was that in the Kingdoms Campaigns and Retrofit Mod(who's stats are based on the expansion's changes) was that spearmen became considerably stronger and able to beat most infantry, only struggling against two-handed weapon infantry, as well as being able to defeat or at least damage cav and soak up cav damage. Also their really high defense and larger numbers made them the ideal AR units, thus why Italian Spear Militia, Armoured Sergeants, and Saracen Militia are the ideal AR units for Retrofit.
"An emperor is subject to no one, but god and justice" -Barbarrosa
"The best fortress a prince can possess is the affection of his people" -Niccolo Machiavelli[This message has been edited by Kilij Ae Varyl (edited 04-29-2013 @ 07:38 PM).]