I've playd on all sides, I started bish and was there for bout 2 months, then joined the AA's who were rook and stayed there for about 7-8months. Have just done a little over a month with the knits.
Bish have most of the newbs but also some great teamwork/horde flying as well as some very successful squads i.e. LTARs.
Knights have the most individualistic players (despite having some very successful squads) which leads to the knits almost never really working together and almost never winning a reset--glimmers of hope are seen, but quickly get dashed much of the time.
Rooks seem to have the most veteran players, some very successful squads and more players who fly together though teamwork on the rooks is iffy at best. Generally I've noticed the Rooks fly in hordes, when they want a base, which overwhelms many of their targets.
These are just general observations from my point of view, other's will surey disagree, but to each their own.