having equal population for swords/archers/hops(chariots) is not balanced, as charliedude said.
you need to take into account the defence values of the units
in relation to the units which would be attacking them (slingers, horses and hops
ignoring myths). because slingers have the highest attack per farm space and hops the lowest you need to have your defence weighted more in favour of distance (more swords) and less in favour of sharp (archers)
obv that only counts if you have no idea what you will be defending (hence the reason it is evenly balanced against the attacks of the best unit of each attack type). if you know that those units are only to defend a siege where the likely attackers will be only manticores then you'd need to get more archers in there or if your attacker is farming somebody with horses then get more chariots or hops in.
i actually agree with jarp though, biremes are best
EDIT:
the maths says that the ratios for a balanced defence are roughly as follows:
swords/archers/hops
.......49/18/45........ (~ roughly 10:2:9)
or
swords/archers/chariots
.......135/191/65........ (~ roughly 6:8:3)