How much single coil hum is acceptable to you?

Interestingly, out of my two Jazz basses - If I solo the neck pup, one of them is pretty silent (even with OD on) and the other one has a bit more noticeable hum. The shielding on both are good, and they are both stock Fender pickups. One is a 2002 and one is a 2014.

Would pickup difference cause a difference like that? Is there something else I should check out? How much single coil hum is to be expected/acceptable?