Stellar Phono Section - MC or MM

Curious on opinions, which sounds better MC thru MC section or MC thru MM section with a step transformer.

You are not going to get a general answer as this not only depends on the cartridge and transformer involved but is also a tonal preference. You can spend $$$$ on a transformer that is well on the diminishing returns scale so I would always start with simply using the MC input. You can always audition the transformer later once you’ve got your baseline.