Penetrating an unarmored destroyer's hull is only part of the requirement. The shell must carry enough explosive to damage several compartments or disable a large space such as an engine room. A larger projectile can devote a greater proportion of its volume to explosive when the casing needed to withstand firing stays broadly the same thickness. Faster traverse and more rounds on target help, but their advantage can disappear if many additional hits are needed. The practical measure is how quickly each gun can inflict disabling internal damage.
Notable Point · 2:08:44-2:10:21
Why shell size changes the time needed to stop a destroyer
Destroyer vulnerability depends on explosive effect after penetration as well as the number and speed of hits.