Why later Type 45s might have used an Italian 5-inch gun

Why might the American Mark 45 have lost to the Italian 5-inch gun for later Type 45 destroyers?

European defence cooperation could favour the Italian weapon, which is also considered a capable gun with useful ammunition options.

For a hypothetical later Type 45 batch, the gun choice is placed in the political setting of 2006 to 2007. Britain wanted to demonstrate continued European defence cooperation after the Horizon program had failed, which would favour the Italian weapon over the American Mark 45. Both guns are considered capable options despite their different characteristics. The Italian gun also offers access to the Vulcano ammunition family and other rounds.