The medal distribution system is as follows:
The amount of won/lost medals is determined by the difference in power of the two opponents.
To determine the difference in power, the game tracks the following values:
Best weapon’s power in each of the 3 categories: primary, special, and explosive
Army power, including special abilities and elite perks (not more than 2 per class)
Rank's power
The difference in the overall power (sum of all 3) is used to calculate the resulting amount of possible won/lost medals.