IMO, you gain plenty from practicing pizz as well; but arco forces you to do two things that are not immediately noticable when playing pizz but will give you a better sound.
Arco lets you hear your intonation in a much clearer way than playing pizz so it will create much better positional knowledge.
Arco forces you to hold your left hand in position for the full duration of the note and makes you think about your shifts as a single motion over a specific period of time which will make your pizz lines sound more connected and allow your bass to sustain for the full note duration.
I guess, from my perspective, playing arco really brought to light any and all left hand issues that I did/do have so I can focus in and really clean it up.
Arco lets you hear your intonation in a much clearer way than playing pizz so it will create much better positional knowledge.
Arco forces you to hold your left hand in position for the full duration of the note and makes you think about your shifts as a single motion over a specific period of time which will make your pizz lines sound more connected and allow your bass to sustain for the full note duration.
I guess, from my perspective, playing arco really brought to light any and all left hand issues that I did/do have so I can focus in and really clean it up.

