Pboutin, the standard DL103 has a compliance rating of 5cu, which is very stiff in the suspension, and actually is the stiffest cartridge in the world, that I know of. The DL103D is a different compliance rating, I think it is 15cu, and is more of a medium compliance cartridge.
The interaction of the cartridge compliance and the tonearm is a fairly important one, which relates to the energy fed into the tonearm by the cartridge suspension as it plays the record. Low compliance(stiff) cartridges feed much more energy into the arm than medium or high compliance ones do. This energy can "push" the arm around, in a microscopic way, and influence the effectiveness of the information retrieval from the grooves. The mass of the tonearm should be selected according to the compliance of the cartridge. This is particularly critical in the horizontal mass component of the arm. Also, in a unipivot, the azimuth may also be affected by this, and be in a constantly changing condition when playing a low compliance cartridge.
In general, I recommend that unipivots be used with medium or higher compliance cartridges, although there are a few unipivots that have some design features that mitigate this somewhat. Arms like the Graham 2.2 have stabilizers which keep the arm a little more stable than other unipivots.
I personally think that the standard DL103 cartridge is much too stiff for a JMW arm, and although it will play the music, I don't think that the best possible performance will be attained with this configuration. I'd recommend a high quality gimbal-bearing tonearm for the DL103. The "ol fashioned" DL103 Art talks about could be either the 103D or the 103, but I think he is referring to the 103D. That is a much better match for the JMW than the standard 103 is.
