What is the preferred cartrige mm or mc and why

@gillatgh
You need to do your homework

I'll add that @invictus005, needs to do his homework too.  Must be a school night...

There is a third choice---the MI, Moving Iron. Grado and London (Decca) both have devoted users. They have their own unique sound, different from MM and MC. And high output, so no extra gain stage or step-up transformer necessary.

The first step in making an LP is cutting a master lacquer. This is done by using a metal stylus attached to a coil placed within a magnetic field. All mounted on a radial-tracking arm. An amplified music signal is connected to the coil and drives it to cut a spiral groove in the rotating lacquer disk. So using a mc cartridge is just the reverse of this process! "As it was in the beginning, so shall it be in the end".

The fact that your cartridge is an MC does not make it superior to MM cartridge (or Moving Iron, Moving Flux etc). It's been said many times and approved by many audiophiles worldwide, not by those people who's buying cartridge by reviews or stereophile top 100 recommendation, but those who dig deeper and really understand the process and testing different cartridges in their systems. This is the ONLY way find what's the best.   

I use both MC and MM, practically i prefer MM cartridges, the best MM cartridges are vintage MM cartridges and they are much cheaper than very bad MC cartridges and probably 10 times cheaper than some good modern MC. But the cost is no object in this experiment, it's fact that decent MM could the the last cartridge, no need to search or pay more for an MC. In most cases the cost of MC phono stage or SUT or MM phono stage +SUT or MM phono stage +HEADAMP is a pain in the ass when it comes to LOMC. Then add re-tipping process and so on. 

The MM/MI/MF has replacement styli, relatively high output, they are neutrial, they are cheaper, they are amazing if you know which one to buy. 

Some reasonably priced vintage MC cartridges are good, but people are crazy when they are buying $3000-8000 MC cartridges without having a chance to audition a decent $700-1200 MM from the 70s/80s in perfect condition.