There is a massive problem with discussing claims that rarely gets mentioned. Consider the following breakdown of losses (figures for illustrative purposes only):
Definitely lost in air combat: 40%
Definitely lost to non-air-combat reasons: 30%
Lost to unknown causes: 30%
Now consider two air-forces, A and B.
A says:
Losses in air combat = 40% + 30% = 70%
Losses to non-air-combat reasons = 30%
B says:
Losses in air combat = 40%
Losses to non-air-combat reasons = 30% + 30% = 60%
Now for air-force A read 'RAF', and for air-force B read 'Luftwaffe' or 'USAAF' or 'USN'. The truth of this is simply beyond dispute, as a glance at the figures will confirm. In the second half of 1941 the RAF lost over 400 fighters in operations over France, of which about 140 were attributed to flak or non-combat reasons. In the same period JG2 and JG26 lost 235 fighters - but allegedly only 103 in air combat. So, to put it simply, either the Spitfire was vastly more reliable than the Bf109, or there was something seriously wrong with the way these figures were calculated. For the Hellcat you have 815 losses, but allegedly only 245 in air combat, and for the P38 1752 losses but only 451 in air combat. I believe the estimable Hop pointed out that according to German records their bombers allegedly suffered a higher accident-rate in daylight operations than during the night, which makes absolutely no sense.
Another point regarding alleged German losses is that we know from other sources that many lost aircraft never found their way into the official lists. Besides statistical analysis we have Ultra intercepts, other German records (eg diaries) and the reports made by the RAF's crash-investigation teams, though unfortunately these teams only began operation in October 1940 when the BoB was winding down. I find it difficult to understand the reasoning that a signal from a Luftwaffe unit saying "We lost 6 aircraft today" is less accurate than figures compiled by some pen-pusher in Berlin claiming only 2 were lost. For what it's worth, my estimate is that the Luftwaffe lost 500-550 Bf109's shot down by RAF fighters during the BoB, while destroying about 450-500 Spitfires and Hurricanes in return.