Eventually the 'secret' was discovered: the bubble canopy of the F-86 provided a distinct advantage to the US pilot over the constrained view offered by the Mig-15 canopy in detecting enemy aircraft. Despite being technically inferior this quirk in the design of the F-86 gave its pilots greater 'situational awareness' — the ability to see the surrounding environment better, detect threats a split second earlier and act before rivals did — giving them a significant competitive advantage.
There is a strong correlation between situational awareness and performance: seeing your environment better enables you to detect opportunities and threats earlier and move quicker. It's the equivalent of being able to look before you leap.