What is the preferred cartrige mm or mc and why

I think Invictus005 is overstating MM's advantages.  Having been through Shure V15's, Stantons, Ortofons, A-T, and Grados, I can state that my Dynavector MC through a Schiit Audio Mani phono stage brings a level of dynamics and transparency that is unrivaled by the others.  The A-T is the only one that comes close, but at the cost of a thicker lower midrange, and less detail.

MM carts sound more "hi-fi" than real.

@atmasphere 

 to get the best out of MM its a good idea to load them correctly.

This the reason why people don't really understand the potential of MM cartridges, their phono stage has ONLY 47k Ohm loading. It must be at least 30-100K Ohm range to try different loading with MM. 

We just have a loading strip on our preamps so you can install anything you want (quite often with MM cartridges, a capacitance is also involved).

Quad had something similar with their earlier pre amps, with removable input boards for cartridges, and tailored boards for many well known cartridges of the day. The tape input board had adjustable settings for sensitivity, and I still use that to avoid clipping on the input by my Chromecast Audio. Peter Walker was a very practical designer.