Active. It allows you to boost as well as cut. When I do use a passive bass, it's almost certainly with some sort of pre-amp.
For a banjo, it definitely has to be active, preferrably Fishman. Regardless of the number of strings.
You can use a Boss LM2 to balance signal levels, but that won't give you control of the EQ. You'd need to put a graphic EQ or something in series.