There are several things that I would say weigh much heavier that his tone.
- Advanced knowledge of "theory" and mastery of the fingerboard.
- His lightning speed, precision and accuracy, all while having incredible phrasing and "feel" / groove.
- The ability to seamlessly combine styles.
- Incredible stamina.
- composition skills that are considered brilliant today
No one had ever approached the instrument like he had.
Simply, there was bass before Jaco, and bass after Jaco.
Those are the 1st things that
quickly come to mind.