I use whatever the song calls for. Sometimes it's obvious and sometimes there is room for judgement. Most of the music I played called for finger-style and that is my primary technique. I would say slap was a distant second and pick was an even more distant 3rd.
Examples (mostly exceptions to my norm)
This sounds like synth bass to me. I felt pick worked better than finger-style. I did not consider slap.
This is finger-style, but I preferred to slap it.
To my ears this is mostly finger-style but it has prominent slap in the fill section. The bass player I replaced played the whole song slap and the group leader asked me to do the same.
Pick
Pretty sure I used pick on this one
Another pick tune.
You are always so freaking reasonable and logical. It drives me nuts. Hah. I'm kidding about the last part