I use picks and have done for some years.
Whilst always being a predominantly fingerstyle player I think some songs just benefit from the pick and its inherent sonic qualities.
I think it's horses for courses regarding pick guage and material. In my experience:
1) a pick with some 'flex' is probably best for root note quaver-type work (KOL, stereophonics covers etc.. We've all got to play them!) This helps to give a nice even sound to the notes.
2) a stiffer/sturdier pick will give better note articulation & definition, in fact you can control a lot of your sound from the pick; but quavers/8th notes will take more effort with this type of pick as you really have to work to get an even sound.
If you can find a pick that gives you the best of both worlds then you're laughing.
My tip is to rob as many picks as you can from guitarists in other bands (or maybe your own band) and see which ones feel most natural and give you a sound that works.
If you can't rob any, you can buy them for pretty cheap anyway.
Quite a few bass players have an 'anti-pick' stance, which I've never understood. After a few minutes of practicing you've got a new style, maybe even mindset, under your belt.
Good luck to the pick warriors,
H&R