I'd go a bit further - a fair fight, in my opinion, is one where there is around a 50% chance that one will lose.
This pretty much sums it up.
The question is, why does a fair fight matter? I would say that the goal is for both players to have fun. Personally I would consider equal ships fun. I like skill being the difference in the fight. For this reason, I've always wanted a 'stock' classification for ships that can be used for sporting events. A new player may have a significant disadvantage, but they also learn the most during fights and will progress their skill level faster than an experienced pilot.