Why massed PT boats could overwhelm an Iowa

Which side has the advantage: one Iowa-class battleship or an equal displacement of PT boats?

The PT boats have the advantage because their numbers and torpedoes would force the Iowa to rely on secondary weapons while facing too many close targets at once.

The Iowa's sixteen-inch guns dominate comparisons at normal surface-combat ranges, but they are poorly suited to swarms of small craft closing from many directions. The aggregate torpedo threat and the burden placed on the battleship's secondary battery once the boats are inside the main armament's useful geometry. Displacement equivalence does not produce tactical equivalence.