The MIGs may not have been much more 'advanced' than US fighters at that time, but it is axiomatic in war that one should attack the enemy at his weak or weakest points. The US fielded a wide variety of aircrafts in the Vietnam War, from the heavy B-52 to the heavy fighter-bomber F-105 to the versatile F-4 to the light and agile prop job OV-10. The North's MIGs usually conduct hit-and-run operations against heavier and less maneuverable F-105 fighter-bombers. Operation Bolo showed that when MIG-21s are faced against F-4s with the -21 the superior maneuverable one, training, tactics and doctrines prevailed. Operation Bolo pretty much shut down the -21s over North Vietnamese airspace for a few months.
Sounds nice but vague enough. I would like to see at least a couple of credible sources that show a couple of armies who shunned access to weapons more advanced than what they were fielding.