The problem with this question is, that there would never have been 'just' an air war. A war would have always included the other forces.
And then the Warsaw Pact would have had an advantage.
There was a tv-programme on air in Germany one or two years ago where they showed a possible scenario and came to the conclusion that the Warsaw Pact would have been a possible 'winner' and it sounded well thought.
Rememer the huge number of tanks and aircrafts in East Germany and Poland, not to forget the Navy.
The NATO would have had difficulties to stop them.
And many people forget, that many soviet types of aircraft where compatible with NATO equipment, so it would have been easy to use NATO airfields, after they had been taken over. And I don't think that NATO aircraft could have been used with soviet equipment.
You might think that training of NATO pilots was better than in the Warsaw Pact. But did pilots in the NATO practised landings on gras strips for example, not to forget that most NATO aircraft would have not been able to land on a gras strip.
What I want to say is that pilots and planes from the Warsaw Pact would have been (maybe) a little bit more flexible and more tough. Although it is not possible to really to compare their training 1:1. Both parties had different strategies regarding that topic.
And don't forget the psychological advantage. Soviet front units based in East Germany where something special. Their standards where high.
Well, just my two cents