The triple turret was more efficient in terms of space and weight than the twin turret, for the same armament. Meanwhile, the risk of a turret hit knocking out part of the armament was relatively small. A ship with more turrets was more likely to take a hit to the turret. It's also worth noting that with a single turret knocked out, a ship with three triple turrets has the same number of guns remaining as a ship with four twin turrets.

A triple turret typically weighed less than one and a half times as much as a twin turret. The USN's Nevada-class battleship mounted ten guns, in two triples and two twins. The twin turrets each weighed 618 tons, the triples weighed 748 tons. A ship with four of these twin mounts would devote 2,472 tons to its armament, compared to 2,244 for three triples; this leaves the ship with three triples with ~230 extra tons of displacement that can be spent on speed or armour, as well as an extra gun. The need for weight saving was key in the 1930s, when battleship building was governed by treaties that imposed strict limits on tonnage. While many navies disregarded these to a greater or lesser extent, they still had an impact.

It's also important to note that triple turrets were also more efficient in terms of space, and in particular, length. While a triple turret was larger than a twin turret, three triple turrets took up less space than four twins. Bismarck, with four twins, was 823ft long; her contemporaries in the North Carolina class, with three triples, were almost 100ft shorter, at 728ft. The armament isn't the sole determinant of length, of course, with hull form (and hence speed) playing a considerable part. However, a ship with three triples could be shorter, or could dedicate more space to engines, secondary armament, and other important things. A shorter ship also required less investment in infrastructure; there was no need to build new dry docks and the like, which had strict limits on the length of ships they could take.