Still, the 20% advantage rule is good to know. But as said, it does depend on troops and morale heavily.
Militia doesn't get the leadership or captain's bonuses that a noble's unit does, but they may get some from a marshal's/lord's leadership (I'm fairly unsure of this though). The archer disparity is pretty much normal, they tend to either win through firepower (which seems to be about 1/4 of an infantry unit's hitting power per turn, depending on wind), or lose a lot when in melee.
It would be interesting to know just how well an archer unit does in melee if it still has high stats and banners. Is a 75/85 archer unit with banners, high morale/cohesion/training just always bad at close combat, because they're archers? Or are they an average infantry unit with a bit of ranged punch as well?
Possibly the wrong thread for the question, but it does link into the above posts.
There's an strange situation of semi-stalemate right now in Dwilight, where neither side really wants to attack due to superior fortifications on both sides, compared to mobile CS available. Which is good in a way, it forces diplomacy and strategic rather than tactical warfare.