Why paired guns repay their added complexity

Should a balanced cruiser design use single or paired gun mounts?

Paired mounts are usually preferable because their extra maintenance and ammunition demands buy a large increase in the speed and weight of fire.

For many medium calibres, pairing guns can roughly double firepower without doubling the mounting's footprint. Twin mounts demand more ammunition and somewhat more maintenance, but that burden is modest beside the added rate and weight of fire. The broader combat principle is to find the enemy first and deliver a decisive volume of explosives before the opponent can respond effectively. The same logic applies to missile defence and attacks on land batteries, where rapid concentration of fire can be decisive.