There are some pretty essential differences between gameplay in M:TW and R:TW, but the AI also tends to behave differently. In Medieval the terrain is more varied, as opposed to the very generic R:TW terrains, and the effects of terrain are very noticable. The AI can successfully position itself on the highground and defend that position in Medieval, whereas in Rome the high ground is so broad that the AI tends to reposition itself off the highground as you approach. I suppose that doesn't have as much of an affect as it should anyways, because the affects of terrain in Rome are very slight compared to Medieval. What's really unfortunate about the AI in Rome is that it often breaks up its army to attack from many directions at once. That means that the player has to start a click-fest to counter, but in the end it's fairly easy to destroy the enemy in detail. In Medieval the AI had more of a tendancy to keep its units together.The problem with less depth of gameplay in battles is that you end up fighting a large number of battles that are short and similar; that gets old pretty fast.