It is possible to criticise every nation's efforts in the field of aircraft and armament (and just about everything else as well). War is a test-bed of ideas and technologies; some work, some don't. The summary above, while containing only a few actual errors, nonethless gives a biased view by concentrating on the weaknesses of the RAF.

How about the German failure to develop an integrated air defence system to match the British one until much too late? The failure to develop proximity fuzes for AA guns? The failure to develop strategic bombers which worked (He 177, Bomber B)? The reliance on vulnerable dive-bombers which were swept from the skies as soon as they met opposition? The failure to develop an effective maritime air arm because Goering refused to allocate resources? The failure of the Zerstorer concept in the Bf 110? (It later made an OK night-fighter, but that wasn't its designed purpose). Being forced to continue with the increasingly problematic Bf 109 because they couldn't get a replacement into production?

For the record, the RAF realised the need for 20mm cannon in the mid-1930s, it was just that the French HS 404 they selected took too long to get into effective service for a variety of reasons. After it did, it was one of the best guns of the war, especially in its Mk V form. The RAF also had a jet fighter in regular squadron service, and in combat, before the Luftwaffe. And they had the finest light bomber and multi-role plane in the war, in the DH Mosquito, which the Luftwaffe never had an answer to. Their strategic bomber force was also vastly more effective than the Luftwaffe ever managed.

On balance, I would say that the RAF did rather better than the Luftwaffe, where it mattered.

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Tony Williams: Military gun and ammunition website