I agree, it's a nice collection as far as the primary material goes.
Certain care however is needed to be taken with that site's articles, as they are very selective, biased and sometimes outright manipulative with the original sources to come to the 'proper' conclusion.
Basically it applies to all three Bf 109 comparisons, which effectively are a cherry pickings of the worst possible Bf 109 tests vs. the best test, or even prototypes on the other side. The supplementary information on the Bf 109 engine ratings, variants availability etc. is seriously manipulated.
It's better IMHO to read the original reports themselves and make your own conclusions.