The medal system is totally weird.
A hit on a player just above your medal count will earn the most medals (mid-high 30s, 40s). A hit on a 140k medal player will earn about mid20s (from my perspective at lvX, 46k). And a hit on a player with slightly lower medals will only earn 18. Hitting a player with much less total medals count will earn fewer rewards again, but carry biggest risk.
So if you look for medal rewards of 38+ medals, you'll be hitting a player with a tally slightly higher than your own. Same for on defence, if you get cleaned out by a player for 38 medals say, they're just behind you in the medal tally.
The same is true for cogs/conflict points.