Hi there from what little I know about this subject as I understand it the advantage of horse artillery was an increased rate of fire during combat, since they could fire and move to a new position on the battlefield more quickly than standard artillery.
Like most I first assumed faster movement over land while on the march making them an ideal compliment to a force designed for speed over long distances.
However from a previous game it has been explained that since all artillery was wheeled and equipped with horses to draw them during march there was no advantage to "horse artillery" in that respect. So then I was wondering in this game how the advantage is manifest? I assume there must be some difference between horse artillery and the standard 6 pounder but I cannot determine what it is.