Eyg

[Ghost of Rom]

EYG, 16 unit army in my experience is better than a 12 unit army with more valour.

This is very true due to flanking bonus's and outnumbering like has been said. But there does come a point where the florins can get low enough where you cant buy 16 units with a decent valor. Morale below 6 for your core units can get very dicey. A good cavalry charge and a routing unit can often scare your whole army into a mass route.

No armour = more effective versus AP?

I think of it more as
"no armor = armor piercers not get to use thier big bonus on us "