Quote Originally Posted by Ciaran
You can still get a lot out of Militia Sergeants if you pin the cavalry down with some unit and rush the MS in from behind. They´ll do a solid job, in my opinion, Militia Sergeants are definitely underrated by most people. If you know how to use them they´re great.
That is the optimal roles for MS. Their armour piercing bonus is great against any armoured troops even pinned cavalry. They don't have the cavalry attacking bonus however, so are not as effective against cavalry as Chivalric Foot Knights or Halberdiers. They're also good for flank attacks on other armoured units such as CSgt.

Urban Militia can be used similarly, to a lesser effect, though they need some upgrades and a good general to make their morale hold.