Is a low output MC superior in sound quality to a high output MC??

Low output serves you more details, more headroom and generally a better musical flow. But to get the best out of it you need a Phonostage with higher gain. High gain and natural sound is a real task. And expensive.

Less windings mean less mass so low output MC's can give you a faster transient response allowing for more detail to be extracted. 

I have had both HOMC's and now an LOMC.  I won't go back to a HOMC again.  But as others have pointed out, the phono stage is critical.  It must be extremely quiet (no audible hiss) at the higher gain levels needed or you can negate the additional musical detail an LOMC brings you.

This low output MC mantra works only in theory, practically High Output MC can be very good or even better. I have tried both and i do not miss my new ZYX PREMIUM 4D with dedicated pre-pre amp, when i use vintage High Output ARGENT MC500HS cartridge.

I’m pretty sure it depends on the cartridge, if you chose between LOMC or HOMC of the same brand then maybe LOMC is better if your phono stage is good for LOMC, but you can find another HOMC cartridge (from another manufacturer) superior to your LOMC for example. It is very personal and system dependant.

I wouldn’t ignore HOMC or even MM in the battbe with LOMC cartridges.
But trust your ears!

Just to add to the confusion take a look at the Soundsmith "Fixed Coil" cartridges.

(anyone know what Fixed Coil is?)

Knowing the lengths SS goes to i would have to believe there is not much downside, if any, to their high output carts

They start around $399
http://www.sound-smith.com/cartridges/fixed-coil/otello

Has anyone tried one of the SS own brand carts? - Tell us what you think of them.

Thanks

"Fixed coil" is a euphemism for what is more commonly known as "Moving Iron".  In MI cartridges a piece of iron is attached to the cantilever, and it is the only moving part. Both the coil and the magnet are stationary, and the iron causes changes in magnetic flux that induce signal voltage in the coil.  Like Peter Lederman says, MI cartridges have lowest moving mass among the three common types of cartridges.

I have not owned an HOMC cartridge in more than 10 years, so I am certainly not up to date on the latest, but before that I owned a Transfiguration Esprit, two Benz Gliders, and at least one Sumiko Blue Point.  None of these sounded as true to life in my system as have any number of LOMC and/or MM/MI type cartridges.  Thus I have come to believe that, as a class, LOMC cartridges are superior to HOMC.  This is not to say that ALL LOMC cartridges are superior to ALL HOMC types.  There may well be a great HOMC out there, somewhere.