http://na.leagueoflegends.com/en/news/game-updates/patch/patch-523-notes
"...along with some revised minion pushing changes."
basically you're rewarded for having tower advantage, your minions take less damage and deal more damage as soon as sometones t1 turret goes down.
in addition to the gold value
Minions
NEW Pushing advantage
Minions get combat bonuses when your team has a level advantage over the opposing team
Comboing with the turret changes above, minions now get stronger to help the winning team press their advantage and close out the game.
MINION DAMAGE BONUS If your team’s average level is higher than the enemy’s, your minions deal 10% bonus damage to enemy minions. If you’ve taken cumulatively more turrets than the enemy team, damage is further increased by 10% for each turret you have over your opponents.
ENRAGE If your team’s average level is at least 3 higher than the enemy’s and you’ve taken 2 or more towers in a given lane, your minions in that lane deal 90% more damage to enemy minions.
MINION DAMAGE REDUCTION If your team’s average level is higher than the enemy’s, your minions take less damage from enemy minions equal to (tower differential x level differential) + 1. This number can’t fall below 1.
IRONCLAD If your team’s average level is at least 3 higher than the enemy’s and you’ve taken 2 or more towers in a given lane, your minions in that lane take 7 less damage from enemy minions