When I started out, I tried playing with my fingers, but failed miserably, so moved on to using a plectrum. Used them up to the late 90's when I pretty much switched to guitar. The favoured pick's for bass were... Dunlop Nylon's 0.73mm.
Used Dunlop Tortex 0.60mm for guitar (the orange ones).
When that band finished, I kind of lost interest in playing guitar, so started playing bass a bit more. As most of my bass "heroes" were finger-style players, I started working on my bass technique, took it back to bas(s)ics, and re-learned playing with my fingers. Still using fingers for bass, plectrum for guitars.