Why a low output M.C. rather than a high output?

The high output MC's I've seen have an output of around 1.6mV.Alot of phono pre's like to see at least 2.5mV which puts the high output MC's in a less than prefered range.You will need a preamp thats up to the task of providing enough gain.

Wiki sais more than you need to know...
http://en.wikipedia.org/wiki/Magnetic_cartridge

More turns means that it is harder to manufacture and more prone to breakage. MOST of the top cartridges are low output. I would have agreed with Metralla until I got a step up from Bob's Devices. My phono stage has plenty of gain but the step up makes a LARGE improvement. See also recent discussions in Stereophile about transformers. Many of the top phono stages have them built in.

audiophile logic is 'no logic'. follow your pre audiophile instincts for logic.

Fewer turns on the coil mean it is lighter. The whole stylus assembly is therefore lighter and hence more responsive.

You don't need a step up transformer if you have a preamp with sufficient gain in the phono stage. Better sound that way, too.

Regards,