#1
Which one's better? Why?
Whats wrong with the other?

I do both, I switch when playing, I use my thumb pick to do tremelo's and such and I use my fingers for string crossings and such.
#2
What is this, the 25749th time this topic has been discussed? And it always ends the same ugly way.

*reported*
#3
No one technique is better. There are many brilliant bassist that use their fingers and many brilliant bassists that use a pick. It's purely preferrence.

Each to their own.