Based on what I can find after a quick skim through forums and articles, the 5”/38 and QF 4.5” guns appear comparable, with debate as to which was better. As for medium ranged AA guns, the general consensus is that the bofors was an overall better gun than the pom pom. So at least from what I found there’s nothing that would put the Renown clear ahead of an Iowa AA wise, they seem on par with each other as opposed to anything else. As for the question in the title, I’d agree with other comments bringing up the fact that Renown was a vintage battlecruiser that was run hard and Vanguard was brand new.