When a Belfast-based anti-aircraft cruiser becomes worthwhile

What is the point of building a British Atlanta-style anti-aircraft cruiser on a Belfast hull rather than using the smaller Dido design?

It makes sense chiefly as one variant in a standardized, high-volume Belfast-hull production system; without that industrial pipeline, the larger hull offers useful capacity but little economic advantage.

A Belfast-sized hull would offer greater stability, a longer service life, more ammunition capacity, and room for more guns than a Dido. Those advantages alone do not establish a good reason to build the larger anti-aircraft cruiser. The proposal becomes more attractive if a yard already produces Belfast-type hulls continuously and can give some of them a different weapons fit. A common production line could then support several cruiser variants. Without that factory-style system, individually building the larger ships offers little benefit in the comparison.