Which MiG?
This is a very interesting chat but one which is unlikely to end in any conclusion. The F-4C has been mentioned by specific version but no so the MiG-21 so it's all very open ended, maybe deliberately so.
I'll chip in my unqualified 'four peneths' worth.
No fighter aircraft ever shot down another one. No bomber ever bombed a target. The people in the aircraft did, using the aircraft and its systems to their best advantage.
In roughly equal aircraft the better pilot will often have the edge. Aspects such as motivation, determination, health, fitness and training all have as much to bring to the combat than simply the piece of metal that they are flying and how fast it can turn.