Cruiser armament has to be judged against the ship's role. A cruiser expected to operate independently needs the hitting power of six-inch guns against surface targets. A task-group defense cruiser benefits more from rapid 5.25-inch fire able to engage both destroyers and aircraft. The Dido class was therefore a specialized fleet shield rather than an inferior conventional cruiser. Italian cruisers were designed for independent action but were repeatedly pulled into defensive work because Italian destroyers could not provide the required shield, reducing the freedom those cruisers were built to exploit.
Notable Point · 57:39-58:46
Cruiser gun calibre follows independent or escort duty
A six-inch cruiser suits independent combat, while a Dido-style 5.25-inch battery makes more sense for a ship whose main task is defending a fleet from destroyers and aircraft.