With one SUT you can't use all MC cartridges, such phono stage is not universal for all MC. It will work for some of them nicely, but if your cartridge impedance is very low (2 Ohm) or very high (40 Ohm) you can't use one SUT for both of them.This statement is false. The use of an SUT depends heavily on how its loaded at its output. This in turn is dependent on the source impedance of the cartridge. Transformers transform impedance and this goes both ways. So you can indeed use a transformer with a 2 ohm or 40 ohm cartridge, but the loading at the output of the transformer will be quite different! And its important that this is done correctly otherwise the SUT will not sound right to say the very least.
Most SUTs made for a specific cartridge are designed to be loaded at 47K by the phono preamp, with that specific cartridge as the input. That's why they appear to be 'Use specific'. But if you loaded that SUT correctly at its output you could use it with any cartridge. This is why Jensen Transformers (some of the very best made anywhere) can be used with any cartridge, and they have a chart that shows what the loading on the output should be with that cartridge.
I prefer no transformer at all; I find that even the best SUTs seem to take something away from the detail, even if they have plenty of bandwidth (which most do). Since I run an all-tube phono preamp, this requires that I use low noise tubes. Its a simple fact that if you have a phono section with direct-in capability, whether it is solid state or tube the active devices have been hand-picked. I've noticed with our preamps that people think they can just buy a premium tube off the shelf and expect it to work. While that is sometime true its really a craps-shoot; even a premium tube might not be as low noise as you might expect. With any high performance audio equipment you have to hand pick the devices. But the result is great transparency.