[Mobhack]

SSI never explained these in their pamphlet that came with the game, other than some bot about high leader ratings being able to "coach" a subordinate who was close by when firing.

I have the code, but have never been bothered to read through tens of thousands of lines to figure out what exactly does what.

So basically, if you're really interested in such details then you could always set up some test scenarios and run a few hundred test runs to see if something has any particularly observable effect or not that is statistically significant over basic experience itself.

Arty command rating (+ experience) is about the only really significant one - on both sides of the firer/observer equation - as regards to speed of calling in indirect fires.

Otherwise - a high leader rating is basically good in some way, but can really be safely ignored by the player other than keeping formation leaders close by firing units (3 hexes or so perhaps).