Using the JC4 HE/M2's in my Jazz bass currently. Absolutely loving them. Nice low's and low midrange with even response string to string and the top end is slightly rolled off but still sparkly when needed. The JMVC's are a snappy, bright, articulate pickup that caters to certain styles of music where the bass is more on the front. I.E Funk, Heavy Metal, Rock. Situations where the instrument needs to cut through other instruments and be heard.
The HE's are closest to that of a Bartolini' pickup, and the JMVC' FE's are closest to that of a Duncan QP, Aguilar Hot, or MusicMan style pickup. It all boils down to your style and instrument that you are planning on using.