What is the “World’s Best Cartridge”?

Both Nagaoka and I must disagree with you about the MM/MI thing. To quote from Nagaoka's website:

The "Nagaoka MP series cartridge", when type number starts with MP, is different from the general MM expression (moving magnet) and has a different MP type (moving permaloy), and the MM expression has a hey magnet on the cantilever. Although instant, the MP expression is more free to move the cantilever than the magnet called the permaloy, what gives a delicate and high output。

I've corrected some spelling errors in the translation from Japanese, but I don't know what was meant by 'a hey magnet'. Nagaoka, Soundsmith and Grado all use a ferrous metal disc or cross mounted on the cantilever immediately inside the suspension grommet, and this moves within the magnetic fields of fixed magnets, and fixed coils. Nagaoka are proud of the kind of ferrous material they use and call it Permalloy, hence the MP designation. See this page for animated illustrations:

https://www.goldring.co.uk/buyersguide

Dear @mglik : Congratulations for those both new cartridges you own.

Your question could be controversial because any cartridge quality performance levels depends on with what kind of quality analog rig ( inlcuding phono stage. ) is surrounded and depends too of each cartridge owner skills for its accurated overall set up.

Cartridges as yours or coming from VDH or Ortofon or Koetsu or the Etsuro or, or, or,... are the best for its owners but at the top cartridge models in reality I agree with @mattmiller : no best but a little different. Every one of us have our own and very specifics targets and priorities with MUSIC/sound reproduction.

Btw, maybe both of your cartridge could be best " serv " by a different tonearm and obviously a different better phonolinepreamp. At both sides you will experience better SQ with both cartridges that the one you are experienced rigth now.

"" To begin, putting the stylus down on the run in grove there is dead silence. As well as the groves between cuts. This silence is indicative of the purity of the music content. ""

Well that per sé means almost nothing for your cartridges. Rigth now I have mounted a LOMC vintage cartridge made by Sumiko that perform exactly that way in that precise issue and not only that this Sumiko is really good and @dover that’s a " delicated " experienced audiophile knows a lot on it.

In the other side, Grado was not the one with the first MC patented principle but Ortofon in 1948 way before Grado existed.

@lewm , you are wrong Nagaoka is not a MM design:

https://www.nagaoka.co.jp/item/cat/record/

https://www.nagaoka.co.jp/product/diamond.html

Regards and enjoy the MUSIC NOT DISTORTIONS,

R.

@mglik : https://patents.google.com/patent/US2591996A/en

The reviewer on your link said:

""" MM/MI has always been superior texturally and always quieter, but has eluded manufacturers’ abilities to produce maximum definition. Not anymore. The brilliant genius John Grado has done it. ""

and before Grado that was made it by Pritchard owner of ADC and Sonus induced magnet cartridge designs and before that he designed for GE. The model I’m refering is his ADC 27 cartridge and even that I did not experienced yet exist the ADC 10E MK4 that other audiophile says is the best Pritchard design.

Levi reviewer needs to learn something about or at least experienced the Pritchard designs before post that kind of statements.

But as you analog has an emotional " weigth " and that’s why we all are here. Nothing wrong with that.

R.

@lewm : Not the MP 500 because Nagaoka has MM models too.

R.

“Magnet on the cantilever“ is the definition of a moving magnet cartridge. In the other hand, I respect Raul’s fund of knowledge.  Need more evidence.