MM vs MC Cartridges

The MP100 will handle all but the lowest output MC cartridges just fine, so if you're happy with the rest of your gear you should be able to determine whether you like a MC cartridge better. I like and use both, and the differences are not always predictable.

There is also moving iron, just to add to the OP’s choices.

I echo Fuzztone. Get a step-up transformer from kandkaudio.com. Your MC cart will get the authority it needs. 

So many more setting options with MC  carts if you have the right phono preamp, like my PS Audio Stellar. So much so that I am in the process of going all MC. Playing MM on the Stellar is like wasting 75% of its abilities. Even so I love hard pounding rock music more than anything else. Perfect for MM many would say, but not for me. Too limiting, just 47 kohms and you better like it. Changing the ohms anywhere from 60 to 1,000 on the REMOTE has done wonders for me as each recording can sound at its best on different ohm setting. Too dark, bring up the ohms, too bright turn them down. Voila.

At first glance your existing McIntosh phono can do it all it seems.

For my first MC cartridge, I chose low output, because the whole idea of MC is to get refined movement/results from smaller/lighter parts.

AT33PTG/II, wide separation, tight channel balance, excellent sound IMO.

I go thru SUT to MM Phono in my tube preamp, you would just go to your existing MP100 and use it's MC internal SUT.

research the relationship of cartridge signal strength and cartridge coil impedance before and after signal boost, some are difficult combos. my .3mv and 10 ohm coil impedance is a fairly easy combination.