Difference between difficulty settings?

[vodkafire]

What about the campaign AI? In my current campaign map the other roman faction are incredibly lazy, conquering only 2-3 provinces by 240 while I have already conqurerd 14(by sea too) playing medium. Now, i'm short on money so i don't want any bonuses or penalties to me but i wan the AI, especially the other Romans, to play more aggressively. It's rediculous to see them be at war with 3 or 4 factions continuously for most of the game and just sit at chokepoints with huge armies, doing nothing but defending their borders and fattening their cities(all large by now). I've got the Gauls and the Greeks infiltrating my borders every turn while the other faction are supposed to have been conquering them.