The 'tube-transistor' enigma by MC carts?

By accident I got to know an guy from Swizerland who has
worked for years as technician (R&D,testing,manuf.etc) by
Benz. I made some joke about 'Zelle',the expresion he used
to refer to carts,by asking if the carts are made by
prisoners? ('zelle' is 'the box' in the prison) He appreciated my joke and explaned to me in 2 sentences
something I never thought about. There are 2 kinds of
'bobins': iron and the other kind. The 'classical example'
of 'iron' is the Ortofon SPU. The advantage: stronger signal and some kind of 'pleasing warm sound.the disadvantage:(more)distortion.
The 'ruby-cross' bobin has (much?) less distortion but can
sound 'thin' depending on the rest of 'the chain'.
This is obviously the so-called 'Holistic' approach ;
aka Rauls 'it depends...'. Me? Because I can't cope with
more then 2 variables at the same time I am for 'simplicity' approch. The best 'definition' of this
approch is from O.Wilde:'I have the simplest tastes. I am
alwys satisfid with the best'. So I am still seaching.
Raul will you please bring (more) light to this issue?

Dear Nandric, I sincerely hope and expect that the Jubilee et al has better than "0.2db" channel separation at any and all frequencies. Obviously, that was a typographical error on your part. But what were you trying to write?

Have you heard both the Windfield and the Jubilee? I am interested.
Dear Lewn, The Ortofon Windfeld has a channelbalance better
then '0.2 dB';the Jubilee better then '1dB'.
The 'typographical error' as you expressed it is even more
awful it is an 'category error'. I was quoting from HI-FI
news and was careless. What am I trying to write? To answer
this question I need a two 'channel separation'. One is
the 'story' about the 'bobbin-kinds' from the Swiss that
I translated from German. The other is the 'story' from
Johanssen,the designer of Windfeld,about the progres from
Jubilee to Windfeld.The bobbin modification from Jubile
made an pricise 'winding' of the coil for the Windfeld; as
the result (0.2dB) shows. So this 'channel' leeds to the
importance of the 'bobbin' and that was the subject matter.
So were we are now? There was an 'embarrassing question'
and then a difficult one. The third is fortunately the
easy one. Yes I am familiar with both. I own the Jubilee
and an friend the Windfeld. The Windfeld is a better cart
but is also nearly 3x more expensive (in Europe). I dont
belive that Windfeld is 'twice' as good. We in the Netherlans have then,I think,an better choice: Van den Hul
is 'next door' (Holland is a small contry) and one gets
'no worry' proposition: retiping,mods.,etc. Van den Hul is
very kind for hes customers.Compere this with sending your
$12.000 Koetsu to Japan,for example.

Raul indicates "bobbin" is synonymous with "armature", just different terms for the "thing" they wind the coil-wire around. Is "core" another synonym?
I ask because there is also the "air core" design, where the coil-wire is wound around — nothing. Thus there is no interaction between the different materials, hysteresis, or "magnetization" of an iron core.
As it was explained to me, the "air core" is wound around something of course, it must be. They use — Ice. The wire is wound around a sliver of ice of the right shape, which then melts away, leaving no core/bobbin/armature at all. Hence "air core". This must be done in a deep-freezer, of the walk-in kind.Fidelity Research used this method in some of their models, as it was explained to me by a FR aficionado I knew many years ago. Maybe he was wrong, maybe nuts — but my FR MC-201 advertises its air-core as a feature that offers lighter moving mass and lack of the interactions mentioned above.
Do any of you know more about this?
I’d like to think he wasn’t crazy. I bought several FR cartridges from him, because of their sound of course, not the ice-theory.
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@bimasta Here is some info translated from Japanese about Air Core Coil of Fidelity-Research PMC-3 :

" Air core coil is adopted as coil, weighing is realized compared to ordinary coil part made of magnetic material as core material, and magnetostriction caused by hysteresis curve of core material is expelled. In addition, by adopting a new special lightweight resin coil bobbin, the total weight of the oscillator is reduced to about 1/3, and the tracking ability is improved.... Samarium cobalt magnet is adopted as a magnetic circuit. This material has an ideal characteristic that it has higher holding power compared with ordinary Alnico type and it is hard to self-demagnetize. Moreover, the yoke part can also be downsized, the cartridge’s own weight is drastically reduced, and the initial characteristics can be kept for a long time.... Precision cutting is applied to the yoke to make the entire magnetic circuit close to a circular shape. As a result, effective magnetic path length can be shortened, size can be reduced, and magnetic flux leakage at the corner portion is reduced to achieve high efficiency.... A 0.04 mm diameter net flow line is adopted as the coil. "