This is a very nice thread indeed
What a long part about the F4 and the Mig 21. I recall reading about dogfights between those two in the Vietnam war. Well, from that source the F4 was definately the faster one, being able to extend and climb while at it, not to mention rapid extension during a dive. However, in a tight mix, the 21 was more agile.
BTW, sometimes the F4 used their brakes in hard combat. And remember, - the F4 is a naval plane as well.
But my vote, it goes to the Spit! I do not agree upon the somewhat naive theory that the Spit saved Britain, - the matter is more complicated than that. You would rather say that Dowding saved Britain, or even more correctly that the RAF did. It is the only time in military history that a planned invasion of a country was stopped by an airforce.
The number of aircraft mounted by the RAF in the BoB was smaller than the French had before the war. So far the LW had crushed all airborne opposition easily. However, during the BoB, they met for the first time an organised and decently equipped force. The LW lost. Only 2 years later, the Brits launched their first 1000 plane bombing raid on Germany.
And why the Spit? Well, although the SpitI was just roughly equal with the 109E, the beast grew well and took the superiority out of the LW fighter jocks hands. It served in great numbers, on all fronts, and was very much loved by its pilots.
Still showing up on so many airshows today, it is also the only WWII warbird that I have seen doing mad aerobatics!
Spitfire it is