Since units get attributes improvement, they are more valuable in battle and tougher to defeat, let players get an adeguate loot.
Comparing an elite unit with a champion unit, their stats are very similar.
here the proposed loot comparison:
Elite Swordman: 15food 10 wood 15 metal 100 xp
Champion Swordman: 10 food 10 wood 15 metal 150 xp
{F124139}
I'd suggest to increase the champions food loot by 5.