Submarine success depends on deployment geography and endurance

In a future war, would a British or American submarine commander sink more enemy capital ships?

It depends on the war and deployment: American boats have magazine and Pacific-position advantages, while British boats may receive more aggressive or longer patrols in some theatres.

The comparison begins with the submarines' assigned theatres rather than treating their captains as interchangeable competitors. American boats carry more weapons and would be closer to a Pacific conflict with China, while British boats could be positioned more aggressively against Russia. The smaller Astute force might also keep individual boats on longer rotations than the larger American submarine fleet. The exchange therefore makes logistics, geography, and fleet size decisive parts of any apparent ace's record.