OC = old client
NC = new client
im a OC player.
what i mean is the mechanics of the game.. the rules etc..
Food. When you conquered someone they would give you metal, oil, and most importantly, food. Your units every tick would require a certain amount of food, if you didnt have that amount of food, your army would starve to death slowly.
There was another type of outpost called a barracks, which was a training base that you couldnt train units on. Units parked on a barracks did not use food.
This added a whole new dynamic to the game as it made conquering colonies and maintaining conquers absolutely critical for you to succeed at all. Additionally, during wars, it made finding and making barracks critical, which gave you another thing entirely to consider during war.
Food required you to put a lot more effort in during peace time and added a new dynamic during war time. I assume it was removed to make the game more noob friendly.