AP vs lethality

[Atraphoenix]

barbaroi has no chance in steppes while nomads have no chance in the middle European forests.
phalanx in the middle both no chance to expand there.
(I do not mean player, AI)
Maybe because of that reason Roman AI is so passive in my campaigns.

P.S. AP is only for heavily armored troops. Lethality is good in general... In fact I do not see much difference. maybe %10 -20 on casualty. So I can advice the size, choose the unit which has more man if AP unit has more man use it if lethality unit has more man use it. Cavalry is mastered by player, AI is not capable of using cavalry wisely. (Phalanx lovers' frontal charge) so I was about to give up fighting with cavalry dominated factions. I got tired battling 1-2 hours of micromanaging.....