Would a British 4.5-inch gun have been better than the American 3-inch/50 for first-generation JMSDF destroyers?
Short answerThe 4.5-inch is more versatile, but the 3-inch/50 is the better anti-aircraft weapon and probably suits their self-defence role better.
NotesThe 4.5-inch gun is preferred as a general-purpose weapon. The 3-inch/50 is judged the better anti-aircraft weapon. On a destroyer intended primarily for self-defence, that gives the American gun the advantage. The choice depends on the expected task.