Both of them are high-speed aerial fighters. The F4 is mainly characterized by its ability to achieve both mid-air penetration and ground attack, while the J-8IID is a high-speed interceptor fighter. They have really extraordinary strengths and weaknesses.

It also belongs to the 2-2.5 generation fighter aircraft. The reason why the J-8IIB is kept is mainly because some potential adversaries still use the F4 as an assist combat fighter.

This is something that even the U.S. Air Force Combat Intelligence Analysis Center has been unable to support. However, mainland Chinese netizens said: "Absolutely impossible," Fin Whale" ( NATO's provocative name for the J-8) F4 improved model far exceeds the J-8IID.