Quote Originally Posted by Gilrandir View Post
As Drone in post #3 remarked, heroically fighting units usually take so heavy casualties that they are reduced to few people that will just dissolve in a mass of zero-value retrained unit soldiers. Besides, how can you be sure that you will get precisely that unit of outstanding fighters back, but not a heap of peasants?
By the way, does the AI return all captured soldiers or only some of them?
All of them.

Come to think about it, while the unit quality might be lower than normal (aka the UM runs easier than the knights), unless they're hit badly by v&v, the runners will at worst be valour 0 and probably higher (some veterans should've survived), so the quality of the ransomed men will be higher.
So quality wise, if your army didn't contain any fodder units, the ransomed men will almost always be better than fresh recruits (and the same quality in worst case scenario).