15-inch triples or 18-inch twins: combat power and deterrence

Would 18-inch twins or 15-inch triples be more effective in combat?

15-inch triples are favoured for combat effectiveness; 18-inch twins would have greater value as a threat to escalate the naval arms race.

15-inch triple turrets are judged more effective in combat at the period under discussion. The case for 18-inch twins rests on their deterrent effect and the threat of escalation. A rival would have to consider whether the next British class would repeat that heavier armament. The larger calibre could therefore influence a building competition even when the smaller guns offered the better fighting arrangement.