I`ll try to explain the question on the 3rd conquest (Fall of Rome)
You have free upkeep for all units.
There are 2 units you can possibly pick from:
Raider:
Attack 2
Defense 1
Cost 10
Marauder:
Attack 4
Defense 2
Cost 30
Now, is it worth to advance to marauder, when your city could produce 3 raiders instead of a marauder?
We do not know, whether our enemy uses legionaries, or garrisons, or if they are even fellow barbarians.
You have free upkeep for all units.
There are 2 units you can possibly pick from:
Raider:
Attack 2
Defense 1
Cost 10
Marauder:
Attack 4
Defense 2
Cost 30
Now, is it worth to advance to marauder, when your city could produce 3 raiders instead of a marauder?
We do not know, whether our enemy uses legionaries, or garrisons, or if they are even fellow barbarians.