It all depends on the relative performance of the planes involved. The more of a performance advantage a plane has, it allows its pilot a chance to recover from a mistake. As the sherlocks in this thread have pointed out, an La-7 vs an Il-2 (or Goon, or Stuka, or Val, etc.) is going to result in an Il-2 digging a hole in the ground.
The closer the performance between the planes, the more pilot skill comes into play. Pee Fiddy Run vs. El Gay Seben will be a closer fight and the better pilot should win, regardless of which plane they are in.
There is no hard and fast ratio that can be determined. As a graph, it would look something like this:
