Hi Vetterone,
I must start by apologising for the slight delay in responding but that was caused by personal demands that kept me occupied yesterday.
Anyway, in responding I should note that there exists too little information on the Glanz and most particularly on the "G" series. This includes the absence of the User Manual, Specifications sheet and test data that often accompany cartridges. That fact played a large part in my starting this thread. Hence, the little I know is still in need of kind contributions such as yours.
As far as I am aware, all the G and MFG series of Glanz and the Astatic MF series are - as you note - moving flux (MF). Of course that does not apply to the MG series of Glanz. Indeed, the literature from France positions 'those Glanz that it covers' as at the cutting edge of design by displaying a [then] new mf technology: "Les cellules GLANZ sont fabriquees au Japon par la societe MITACHI Corporation. Ces cellules sont dites a flux variable (Moving flux) nouveau procede dont le pricipe est le suivant..."
I should note that this technical commonality should not be seen to make the cartridges the same. As you note, THEY ARE CLEARLY NOT. It would be the equivalent of classing a Rolls Royce as the same as a Morris Minor because both share a combustion engine!! Equally, there appears to be no original literature treating of the G3 and G5 models. And so I can only discuss the differences that I have observed.
All of the G series [G1, G3, G5 and, ultimately, the G7] share the same fixing method and their styli are interchangeable and bear their common number: meaning they are the M1, M3, M5 and M7 styli, respectively. The G7 and top of each of their cartridge range [G7, MFG-71L, MFG-51L, MFG-31L and MG-70L] all use line contact stylus. All others use elliptical styli. This is an obvious difference concerning their performances.
Furthermore, even a cursory glance at the top Glanz G7, G5 and the Astatic MF-100 shows obvious differences. There is, for example, a conspicuous difference in materials used for the cantilever and its housing. But it is with regards to performance that you are correct to note the most important distinctions.
The Astatic is a very good cartridge but I do not feel that it is in the same domain as these Glanz. Coil windings, materials used, coupling mechanisms and output are distinct across them. And the G7 is, as you note, rated at a whopping 4.2mv. For testing purposes this means that you have to elevate the gain/volume control in order to place the other two on an equal footing when it comes to sheer scale and definition. The Glanz are simply better at retrieving detail than the Astatic and the G7 is better than the G5 on this aspect: once correctly set up and run-in!
Regarding the differences within the Glanz G series, the power and detail superiority of the G7 over the G5 is therefore not only down to their distinct output powers nor is it down to their distinct styli. This is easily tested by the noted volume alterations and by interchanging the styli and testing on both cartridges.
Incidentally, the G7 comes as close to repeating the accuracy that I detect with my Technics P100c MK4 as any cartridge I have heard. The most notable difference between the two is the Glanz's transient speed and dynamic impact. If you need a platform from which to best explore this distinction, there is no finer place than Solti's Mahler 8 (Decca). Due to the physical laws affecting the volume of sound on such a large and sonically complex work, this box set is one of the most difficult to replicate within a listening room. The G7 comes as close as anything I have ever heard. There are nevertheless delicacies with the Technics (on a Morch DP6) that I have also not heard replicated anywhere else. Conclusion? Both great cartridges but different.
I hope my slight knowledge proves useful and that further contributions are forthcoming.
As always