Why there is no single best Second World War submarine

What was the best submarine of the Second World War?

There was no universal best: Gato suited the Pacific, while smaller boats such as the U class could be preferable in confined seas such as the Mediterranean or Baltic.

The Gato class is preferred for long Pacific operations, with T-class boats as another strong oceanic choice. In the confined Mediterranean or Baltic, the smaller U class is more suitable. Range, size, endurance, and operating environment matter more than declaring one universal winner.