Why K31 favoured 6-inch guns

Why was a K31 design with twelve 6-inch guns better than a K25 design with sixteen 5.25-inch guns?

The 6-inch design used fewer, established turrets and avoided the topweight, mechanical, and ammunition-handling burden of eight twin 5.25-inch mounts.

Using a familiar four-turret 6-inch layout keeps ammunition handling and turret machinery manageable. It continues arrangements already understood from Town and Crown Colony-class cruisers. Eight 5.25-inch turrets add substantial topweight, mechanisms, magazines, and loading systems. The smaller calibre produces the more complicated ship because twice as many powered mountings must be supported high in the hull. The closing warning is that naval staffs also produced design studies to demonstrate why a configuration should not be built, so a surviving drawing is not proof of construction intent.