Well, I can't compare to the NJ-4's, but I can compare to two different sets of Fender singles, as well as a set of Barts. I'm the guy who left the last post in the Nord pickup forum, 'Dual coils & Fat Stacks.'
Since the post (2 years ago) I have gone passive, and changed to a maple neck. But the essential differences remain as before.
To recap in 1000 words or less: I was a dual humbucker guy forever, like 20 years.
Decided I wanted the Jazz tone. Built a parts jazz, with an East pre. Hated it. Couldn't get a 'fat' sound no matter what. Humbuckers spoil you with that pillow they produce.
Didn't realize at the time that my problem was due to my approach to the instrument, which needed to change in order to get a good Jazz sound. Looong learning curve, I discovered.
I tried the 3 different above mentioned singles(actually the Barts are humcans). No result. Very frustrated.
Went to Winter NAMM 2007 and found Nordstrand. Stew or somebody was wailing away on a Nordy with Fat Stacks and an Aggie pre. I almost fell over at the sound. Collected business cards.
As soon as I got home I ordered a pair. Routed and installed. Much, much better. NOW we're getting somewhere.
Still took awhile to come to grips with the sound, but eventually I came around and now wouldn't trade them for anything. I can even get a good sound with 'normal' single coils now!
Bottom line: They are a single coil pickup(OK stacked, never mind that) and as such sound unmistakably like ordinary single coils, but fatter, as you would expect. Less 'clicky', I guess. Thicker. More 'forgiving.' They are very bright and deep in single coil mode, and slightly different in dual mode-less highs and lows, and lower output. Still very nice. A different harmonic structure than 'normal' singles, but killer. A convincing Marcus tone is available if you can do it. But it's slightly different, for sure.
