IMO, and this is ONLY my opinion (not stating as fact), is that there is not any advantage to a SUT in the better phono stages. My preference is the MC input rather than an SUT into a MM input. As far as I'm concerned, SUT / MM input combo is only for those phono stages with deficient low-level MC input sections.
I cannot say I've made a direct comparison of a MC through a SUT into the MM input against the direct MC input in my system. But I find the MC input in my phono stage quite excellent and better than anything else I've heard.
I cannot say I've made a direct comparison of a MC through a SUT into the MM input against the direct MC input in my system. But I find the MC input in my phono stage quite excellent and better than anything else I've heard.