EAR 834P Deluxe with Dynavector 20 HX H output Cart.

So don’t you think, if EAR make a great SUT, that the SUT built into the EAR is very likely to be excellent? Plus, it does away with the need for an extra set of RCA connections and an extra pair of external low capacitance RCA cables to connect an external SUT to the EAR MM inputs. Those advantages alone might more than make-up for any difference in quality between an external EAR SUT and the built in one.

That is good advice, IF the HO version of the cartridge is as good as or better than the LO version.  Unfortunately, this is usually NOT the case.  Usually the LO version of an MC cartridge that is available with high or low output, is superior.  Then it becomes a matter of personal preference whether one likes that LO version into a SUT for added voltage gain, vs the HO version directly into the MM stage. Unfortunately, no one here can tell you which set up you would prefer.  But I would take advice from those who own the same phono stage and either the LO or the HO version of the same Dynavector cartridge.