Arcade top tier aircraft

Before fox 3 missiles were introduced usa aircraft were consistently highest kill ratio on leader boards 9m far better than r73 in my opinion. Now fox 3 ,it seems aim 120 is superior to r77.
Now noticing gap widening even more on leaderboards in this short time. I understand usa aircraft are mostly superior but their is a clear advantage visible and it aint a skill issue.
Any thoughts.