Recently I built 2 identical kits which gave me a chance to do some good comparison tests. Both kits were YB-4 bass with standard hardware. The only mod was replacing the standard jack with barrel jacks.
One kit I used the wires that came with the kit. The other I used expensive shielded cables. There was no noticeable difference although both of them suffered from slight background noise. It wasn't a grounding issue because touching the bridge eliminated the noise.
I decided to add copper shielding to one of them. I chose the one with shielded cables. Inside the pickup cavities and lining the control cavity including the back of the cover plate. Bingo! No more background noise.
I did the same with the other kit and got the same result.
I always thought the wiring was more important but in future I'll be paying more attention to shielding.