Hi,
For me all methods are valid, as I think that all depends on song, style and sound, etc... So, I am more impressed with creativity, musicality and versatility, than any specific technique.
The breakdown for me:
Fingers - 50%
Pick - 40%
Slap - 5% (not good at it really... but can be fun)
Others - 5% (Ebow, playing chords and arpeggios finger picking/classical guitar style, occasional tapping, etc...)
Also, I think that depends on the EFX that you are using. I always prefer to use a pick when using any form of Overdrive, Distortion or Fuzz with the bass.
I am also considering getting a upright/cello bow, as I saw the guy from the The Airborne Toxic Event using a bow on a P bass to great effect a few weeks ago, and this as given me a few ideas....
Cheers,
Joao