Well, the Japanese AA on ships wasn't terribly effective. Their heavy weapons were ok and the 3.9in gun they were deploying late in the war was very good. However, the lacked any adequate medium or light weapons and their 25mm and 13.2mm weapons were totally outclassed by the 40mm Bofors and the 20mm Oerlikon. In short, I would rather face Japanese flak than German flak but the Germans were definitely more humane in their treatment of POWs (excluding the Russians) than the Japanese.