Sloehand, what you have said is true in small samples but a complete croc in terms of data as large as this. I fly for bish now, so I am not being biased. What Zazen's data indicates is unmistakable proof that both rooks and knights are (by the scoring standards determined by HTC) better fighter pilots. Unmistakable.
Mass statistics are not "a joke". There is an entire statistical significance formula that proves otherwise. If we had the raw numbers of the data provided (ie how many pilots were involved, how many kills were recorded), I am sure we could prove statistically to at least a 95% confidence level that the data accumulated is not random.
Furthermore, what you're saying is questionable even on sort of a philosophical standpoint. If all those "good" bish pilots are flying rook and knight and accumulating stats for them, are they even bish anymore? The same goes for rook and knight pilots flying for bish. One might argue that you are only associated with the country that you are accumulating stats for at any given moment.
It may seem to you to be a better choice to rely on anecdotal evidence, but even that can be broken down into statistics. If we took all the ancedotal evidence in this entire thread, and rated fighter skill on a scale from 1 to 3, 1 being lowest 3 being highest, it seems to me as if the ratings would still be (lowest) bish, knight, (highest) rook. Anecdotal evidence in this thread seems, to me, to just be backing up what the statistics are saying.
This may seem disturbing or offensive to bish pilots that they are being labeled as generally poor in their fighting ability. Well, all I can say is to compare only yourself to your opponents. You do not represent the entire country you fly for. I have spent a good deal of time flying with every country, and I really enjoy flying with the bish, whether or not the stats say they have a lower K/D. I have flown with some very skilled fellow bish pilots. And I have seen below average pilots flying for every country. What's best is just to keep continually learning the game, enjoying the company of the people you fly with, and having fun.