Apart from the SUT or high gain Phono Stage there is a third option such as Headamp (or Pre-preamp).
SUT is passive
Headamp (or Pre-Preamp) is active device
If your MC phono stage can’t handle your LOMC cartridge or you’re not satisfied with the quality, you can use SUT or Headamp and MM phono stage.
You have to pay more attention to the amplification device if your phono cartridge output is less than 0.25 mV, if it’s higher then you may never need a SUT or Headamp and most of the MC phono stages have enough gain to handle your LOMC cartridge.
Still you may like different flavor of the SUT (or headamp) in comparison to the high gain MC phono stage.
As you know each phono stage is different, even of there is a gain for LOMC it does’n mean it’s better than another phono stage + SUT.
"Current-injection" MC phono stage for low impedance MC is something special, it can be much more impressive than conventional MC phono stage.
Noise is not the issue when you're using quality devices, no matter what type.
Normally with a Phono Stage you have optional loading for your MC cartridge and you can change it right on the phono stage. To do that with SUT you will have to change SUTs
SUT is passive
Headamp (or Pre-Preamp) is active device
If your MC phono stage can’t handle your LOMC cartridge or you’re not satisfied with the quality, you can use SUT or Headamp and MM phono stage.
You have to pay more attention to the amplification device if your phono cartridge output is less than 0.25 mV, if it’s higher then you may never need a SUT or Headamp and most of the MC phono stages have enough gain to handle your LOMC cartridge.
Still you may like different flavor of the SUT (or headamp) in comparison to the high gain MC phono stage.
As you know each phono stage is different, even of there is a gain for LOMC it does’n mean it’s better than another phono stage + SUT.
"Current-injection" MC phono stage for low impedance MC is something special, it can be much more impressive than conventional MC phono stage.
Noise is not the issue when you're using quality devices, no matter what type.
Normally with a Phono Stage you have optional loading for your MC cartridge and you can change it right on the phono stage. To do that with SUT you will have to change SUTs