@artemus_5 It isn't a cut and dry question. When using an active stage for MC with increased gain, one has to either design a separate preamp with added open loop gain or there will be a compromise between the two gains, that is, the gain for MM and the gain for MC. This usually isn't an issue with selectable gains for MM, since the gain changes are usually small.
Another issue is electronics add noise to the music signal with degrades the coherence of the music. Granted, there isn't much we can do about that, after all, everything will get amplified sooner or later. But the smaller the signal voltage, the more susceptible it is to noise degradation.
I've designed preamps and some of them have had MC gain selection switches, so I am well aware of the issues here. Granted there are good preamps out there with selectable gains for MC and MM, but for me, the SUT injects no electronic noise because it has none, which is a big advantage. After that, it becomes which is a better design, so one cannot blanket statement and say SUT's are not as good as a preamp with selectable gains. In many cases, the opposite is quite true.