You commented against the "it's the pilot, not the plane" quote (which I have agreed with you on for some time, by the way), and explained why it wasn't so easy to say that.
This falls into the same category. Simply stating "the rooks kill more" is a gross oversimplification of the matter and doesn't take into account all the reasons WHY.
SHawk for example, has a very high rank and kill/death ratio, but most pilots when they catch him without his 10 escorts have been able to kill him quite easily.
Rooks usually come in from the stratosphere, in great numbers, and bounce/vulch cons on the deck, and run the second anybody comes in from another field with enough alt to contest their presence.
That is really a lack of skill being rewarded, more than showing they HAVE skill.
Bish tend to spread out, they have their hordes (as do knits at times), and usually tend to fight it out when engaged. They like their missions, that's for sure.
Knits... well knits are annoying as hell at times. Herding cats would be easier. As a team they leave a LOT to be desired. I'm flying knits for squadron consideration, but before joining this squad I did rotate. I hold no loyalty to an arbitrary chess piece. We can come in low or high (to be fair most I see seem to be mid-range, 8-12k or lower), and sometimes we can horde but generally it's not because of giant missions intended to smash opposition, it's more like a flash mob.