Quote Originally Posted by Procrustes
I pile the armor upgrades on my mounted sgts, too - it slows them down, but I figure it keeps them in the field a little longer.
Armour does not slow your units down directly, though it does make them tire faster in the desert or when it snows.

I like light cavalry as well, especially mounted sergeants, but I prefer horse archers. They are faster and can really disrupt your opponent. Of course, you need other units to exploit the disruption since many horse archers are weak at melee combat, but nothing is so satisfying as turning a well-organised enemy army into two or three disorderly masses and then charging in with heavy cavalry.