IMO, the APB is not a good "standard": it is the strongest ranged weapon in the game, with 85% of the range of "artillery" guns.
The DUC is a much more reasonable weapon to compare with: average range, average damage, available early.
(I "fixed" the APB early in my mod)
A smallish Main Gun for one of the capital ships would be good to use here.
Then you get the long-reload heavy guns on one side, and the rapid-fire close-in guns on the other.