The use depends on the unit, and what I'm hiring them for.
Some might be intended to act as city guards if I can't recruit any there, and then I just, of course, aim for the best price-quantity relation.
Some mercs I might hire to act as catapult fodder/for specific combat reasons, and they'll probably get sacked after the battle (if I see no use for them anymore).
However, some mercs I might use for longer periods of time, and this includes, for example, Toxotai Kretikoi (which you can, even retrain as several factions, no?), and such otherwise unavailable troops (I might need more cavalry, for example, and have no access to recruitable types).
Of course, I prefer factional (trainable regionals included) over mercs, because of the aforementioned chevron-gaining and retrainability.
Bookmarks