That would need a definition of "a Shiina track", which would probably vary very much throughout these forums.
SS and KZK are from entirely different worlds to me, so that makes a comparison very hard. With SS she reached the peak of where she started out, and the bulk of the songs were written by her as a teenager. So with SS she tied those loose ends for good - with KZK she went beyond that "rock persona" and created something utterly genuine.
So for me it's always almost like comparing albums from two different artists... but KZK for me, no question there.
On a side note, I'm totally sure I'm going to be the last person to hear Sanmon Gossip on these forums.