Below are three clips of Percy Jones, respectively from early Brand X (playing a fretless Fender Precision), later Brand X (playing a fretless Wal) and finally Tunnels (playing an Ibanez piezo-equipped Ergodyne custom). My observations are that (1) it really is in the fingers as Percy sounds like Percy (and noone else) whatever he plays and (2) that the good old fretless P delivers the nicest, woodiest tone of the three (in Percy's hands the Wal is more middy, the Ibanez very dark and buzzy; I do appreciate the Wal can be much more versatile tonally than displayed here).
Fender Precision
[media]http://www.youtube.com/watch?v=7OqQ4m84FyY[/media]
Wal
[media]http://www.youtube.com/watch?v=IenEUOxLNlU[/media]