Distinction between MM and LOMC stages in a phonolinepreamp are mainly that the LOMC cartridges needs at the same time: very high gain ( some times over 80dbs of gain. ), .very low generated noise level and with low distortion level.
Units for MM/MI has around 40-45db on gain. Only for you can imagine what means that very high gain for the LOMC cartridges: doubling the power gain gives you only 3db of additional gain.
More gain means higher noise and level distortion and needs deep knowledge level and skills to design that phonolinepreamp to mantain that high gain with noise/distortions at minimum. That's why is really dificult to find out good phonolinepreamps that can handle with " no compromises " LOMC cartridges using active devices and when you find out comes with very high price tags.
Drawbacks ?, all cartridge designs it does not matters if LOMC/MM/MI comes with its own trade-offs.
If you have the rigth audio system, money and know-how levels to make the whole room/system set up and music/sound knowledge and enough " software "/LPs the best choice is LOMC cartridge alternative. Period.
If not then stay away from analog and go to the best alternative that's today digital that comes with very high quality performance levels even over the best analog alternative you can achieve.
Regards and enjoyb the MUSIC NOT DISTORTIONS,
R.