A couple of points need to be made here. First, I was very surprise that both the French and Italian powerplants rated as well as they do, although I knew that the French design was very compact. I would guess, however, that these plants were harder to maintain than the American and British plants. The Italians in particular would be close to their bases, and thus could afford to have more cramped machinery spaces because repairs would not have to be carried out at sea as often (this is a characteristic of many more 'coastal' navies, including the modern Russian navy). American vessels (and British, too, I would suspect) tend to devote more of their internal volume to repair facilities and accessways, which makes for a less compact, but more maintainable vessel.

Second, ships like King George V and Vittorio Veneto are penalized here for sea-keeping, which isn't completely fair. King George V (and indeed all British capital ships until the post-war Vanguard) were designed to allow zero-elevation fire of the main battery over the bow. It isn't surprising that the lack of sheer forward that such a design requirement entailed resulted in her being a very wet boat. Vittorio Veneto was designed to fight in the more confined waters of the Mediterranean, and thus didn't require the sort of sea-keeping abilities of her blue-water foes. Bismarck, too, was not as good a seaboat as her size and beam might have suggested; she was wet forward, probably due to her being overweight. Iowa, for all her speed, had a very long, fine bow structure, and tended to bury her nose in rough seas.

As far as combat radius is concerned, Italian vessels generally would not be fighting at extreme distances from home, meaning that their relatively low radius of action was understandable. For their part, the British counted on their vast worldwide network of refueling stations to compensate for King George V's shortcomings in the fuel efficiency department, although operationally this may have been a greater liability than the British had anticipated, particularly when more of their capital ships began to operate with the Americans in the Pacific near the end of the war. By contrast, American and Japanese vessels were designed to operate in the vast reaches of the Pacific, although you wouldn't know it by looking at Yamato. She was a fuel hog of monumental proportions, due to her very conservative propulsion plant design, and this greatly hindered her usefulness in wartime because it was hardly ever worth the fuel to drive her out of Truk. Iowa, on the other hand, was possessed of tremendous endurance.