Which was the best fighter: the Bf 109E-4 or the Spitfire I?

If we want to have an objective answer, we need objective fighter comparisons which demand complex analysis:
1. We need to define specifically which fighter models we want to compare. In this case, August of 1940: Messerschmitt Bf 109 E-4 and Supermarine Spitfire Mk Ia.
2. We must specify which arenas (or major categories) will be included in the comparison and which will be excluded. We will only compare the performance in the ‘Combat Arena’, and we will exclude all the others: the ‘Factory Arena’ (where things like manufacturability are included), the ‘Base Arena’ (maintainability, reliability, etc.), the ‘Transit Arena’ (i.e., range), and the ‘Development Arena’ (i.e., capacity of improvement).
3. In the ‘Combat Arena’ we will select the attributes that were most important for fighter pilots (we will use famous test pilot Eric Brown’s attributes) and of those we will only use those where reliable data is available. You can find them in the cards shown in the picture.
4. We will assign a weight to each attribute (again, see the cards)
5. We will use the benchmark comparison method where one specific model (in this case the Bf 109 F-2 that appeared in 1941) is given a mark of 10 in every attribute and the E-4 and Mk. I will be given a score better or worse than the F-2. To obtain a proper spread, a statistical algorithm was designed to compute the differences.

The conclusion is that both the 109E-4 and the Spit Mk I were comparable. Both received a global score of 96 even though there were differences in some attributes. This is one of the reasons there is so much debate.

Both were inferior to the 109 F-2 (not surprising since this model appeared some 7-8 months later) which has a score of 100.

Both were superior to the Hurricane Mk I (the card is not shown) which has a score of 94.

You can modify the weights and do your own calculations too!