Whether you wanna use picks or fingers, its a personal choice.
Note that all these affect tone. Even different picks give you different tones. I prefer using them transparent acrylic picks, the Dunlop Big Stubby 3.0mm. Acrylic gives a brighter and snappier tone. If you use Jazz III's, its material tends to sound less bright and more mellow. So yeap, usage can vary per individual and even per song!