I’ve played Jazz Basses in a variety of configurations for nearly 4 decades. My ‘62 has AlNiCo in it; of course. Most of the rest of the stable have various other technologies going on.
About ten years ago, I was gigging a Sadowsky RV4 in a Big Band. I believe the original pickups in that bass are AlNiCo; but, I could be wrong. In any case, I had recently sold a Suhr era Jazz Bass, and was looking for big slug pickups to try out. So, by chance I got a set of the Delano JMVC pickups, which have large ceramic slugs. Those went into the RV4 and off to rehearsal. Midway through the first tune, the Band Leader stopped all 25 musicians, looked at me in the back, and asked me what the heck I had done to make the bass sound so absolutely amazing. I was floored.
Fast forward, and I now have JMVC’s in several of my instruments, including my NYC Sadowsky, which I specified intending to capture everything I’ve learned to look for in a Jazz Bass.
Roger & Co were perhaps a bit taken aback when I asked them to switch the JMVC’s from the RV4 to the new bass; but, they were pretty good about it. I’ll admit the appearance is a bit startling. I’m more concerned about tone than appearance these days. These pickups, contrary to all the popular hullabaloo about ceramic pickups, sound phat and remarkably old school. The clincher is that the neck pickup, normally a bit weak on the AlNiCo singles, does a very credible job of slotting somewhere between a 55 P Bass and a 58 P Bass. Very useful.
More recently, I acquired a 2008 Fender Jazz 5 Deluxe, which came loaded with the Fender Noiseless pickups. Some kind of SmCo alloy. Those sound absolutely terrific with a Sadowsky preamp; so, the JMVC’s I had bought as intended replacements are still in the drawer.
IME, there are great and not so great pickups. I can’t connect those two classifications with the materials used for the slugs.