Favorite DD gun caliber?

In general I don't really use the increase caliber function on my guns, I don't have much of a use case for it apart from minute min maxing.

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I'm still in 1929 in my Italy game (DIP), and have used 3" guns on my earlier destroyers until I started encountering transport ships with 4.2", so I switched to that for the last 20 years in game. So far my DDs haven't lost a gunfight against other DDs, but I'm now seeing 4.3" and even 5" on armed transports and am wondering if I should up the guns again