The main difference was that MiG-21 wasn't pushed as low-altitude aircraft with strike mission, like what was involved with F-104G. It had quite explicit histo

The main difference was that MiG-21 wasn't pushed as low-altitude aircraft with strike mission, like what was involved with F-104G. It had quite explicit history related to the Uragan project (networked interception system with ground control against US bombers), but while it could be pushed into low-altitude attack role, it wasn't really sold as one. A lot of the remaining issues were essentially shared across both sides due to how early the technology base was, not just on the fighter jet, but for example because you might have to land a high approach speed plane in low visibility using only 2xNDB system (which essentially just gives you correct heading, you have to use dead reckoning for altitude adjustment - an ex-21 pilot said that landing without visibility often involved prayers till you felt tires hit the runway).