The conventional wisdom is that MC is better if you've got the $$$ to invest in a high quality phono stage and tonearm. MC cartridges are also generally more expensive.
If you're not thinking about getting into super-duper phono amps and space-age tonearms, go with MM.
There's also a third option, the high output MC cartridge. You can use one of those with your preamp set for MM.
Cheers
