Ok, I tried to make an "experiment".. as objective as I could. Take 2 pilots. Pick 2 planes. First set of fights is plane A vs plane A, second set of fights is plane B vs plane B. Third set of fights is plane A vs plane B.
First guy I got to do it we picked Spit 9's, then F4U-1Ds, then Spit 9 vs F4U-1D. I didn't get the results I expected. I won the 3 fights in the Spit 9, then I won the 3 fights in the F4U. Then I won the 3 fights in a F4U against a him in a Spit 9. So, I told him what he had done wrong, and hopefully that'll fix that.
Second set was a little better, from my point of view. We did La-7s, then P-47s, then P-47 vs La-7. Since I won the 3 fights in La-7s, and the 3 fights in P-47s, I flew the P-47 and he flew the La-7 for the 3rd one. We did 4 fights, I augered once and got shot down 3 times.
Third set was Spit 9s and 190a5s. I lost the spit 9's 1 to 2, lost the 190a5s 1 to 2, won in the spit 9 vs 190a5 3 to 0.
So, I feel comfortable in saying that it is the plane, and not the pilot that is the deciding factor in a 1v1 fight, with one caveat- both pilots have to know how to use their planes effectively. They don't have to be the worlds greatest stick, but they do have to know what advantages thier plane has over the enemy plane, and how to make use of them.
YMMV, of course.