Provided that they are competent and equal pilots, and the 109E does not start with more energy, on paper the Spit MkI wins the 1vs1 a majority of the time. The 109E wins are going to happen when the Spit pilot makes a fatal mistake, like a bad overshoot across the 109E's gunsite. The Spitfire can win even when the 109E pilot makes no mistakes.
Perhaps true, but the planes are so close in performance that the fight will almost always be decided by pilot skill (or, as you say, initial energy states). Even with two truly excellent pilots at the controls, you can never be sure which plane will win.
For my money this is what makes the Spit I v. Emil fight better than the Hurri I v. Emil. The Hurri can easily out turn the Emil; the Emil is much faster than the Hurri. Pilots flying these planes to their strengths may never conclude their fight, because the Emil can't get guns on the Hurri, and the Hurri can't get in range of the Emil.
- oldman