High vs low internal impedance cartridges....Is there a sonic signature for each type?

Hi Jim, I have a tendency to like lower impedance cartridges like the Air Tight. The lower impedance cartridges use smaller coils (shorter wire runs) usually made of gold or plated copper. The result is a lower moving mass. I think the only attribute that these cartridges have in common is a higher degree of detail and transient performance. Otherwise, they can still sound quite different from one another. You would think their tracking performance would better but I can not say I have notice a big difference. 

Interesting question.  One would think that the low internal coil impedance group of LOMC phono cartridges would all be lightning fast and punchy, but this is definitely not always the case, not by a stretch.  Detailed, airy and open most often, yes, but sometimes a relaxed sound as well.  It just depends on the manufacturer. 

Nearly all my favorite LOMC cartridges are low impedance, typically 2-3 Ohm. Low impedance cartridges must be used with "current-injection" phono stages designed for low impedance cartridges, this combination is mind blowing. 

The problem is about ''moving mass'' on one side and ''core'
versus ''coreless'' coils on the other. Reduction of moving mass is ''obvious'' by reduction of (wire) windings on the coil former. The lower the number the lower impedance but also the output. To increase the output ''iron core'' is usually used  but has as disadvantage ''magnets saturation''. That is why ''coreless'' coils are used.
This however reduces the output which causes phono-pre problems and /or the sense of SUT's use.

magnets also differs - the most sweet one is alnico, the intermediate is samarium cobalt, the strongest one is neodymium. 
Although if you will look into the picture core moves in magnetic field made by permanent magnet (or field coil but that one is exotic) and less turns makes output more homogenous  but signal/noise factor takes over.  Also most of cheap aircores or in other words coreless coils are bass shy...
But IMO if you will look into core of the problem why we do like old designs fastest/easiest answer is the use of neodymium magnet in cartridge designs from big manufacturers like AT, Ortofon, ZYX, Lyra etc.