So I ordered, received and shaved with a handful of samples from M&McN, and I feel like I can now share my experience.
1) In terms of performance, all 4 soaps I tried were top notch. Even with my most aggressive razor, these protected well and provided ample glide. If I had to compare these soaps in a way this is useful, I would say that the samples are very very soft soaps (almost cream consistency) that make low-structure lather. That puts them performance-wise in the same bucket as B&M Reserve and Declaration Grooming Bison Tallow both in the way the soap is picked up by the brush, how much water it needs and the consistency of the final lather. Given that this lathers easily, I think the comparison to DG is better than B&M (B&M is harder to lather correctly IMO). Based on this, I can see these soaps be part of my top 3-4 soaps for sure.
2) The scents were all very well-composed. Crann Bethad is instantly recognizable as a Creed Green Irish Tweed clone (or Davidoff Cool Water). While the scent is very well done, I am not a fan of the Aquatics, so for me, this was a pass. Green Man smelled EXACTLY like B&M Reserve Fern. Didn't love that one either because it has the same slightly artificial smell to it that I get in B&M Fern. AGain...well done, but not my cup of tea.
The two scents that I thought were head and shoulders above the other two were Mandate from Heaven and Ourobouros. Mandate from Heaven also reminds me of a cologne, but I can't quite put my finger on it. Either way, it is super pleasant and unlike anything else in my den. Ourobouros is this really deep, layered scent that bursts with woody patchouli and amber notes. Almost like entering an old wooden shrine/temple in Thailand or Indonesia. Super unique scent, as well, and I just adore this for colder weather.
So right this moment, if I buy full pucks, it will be Ourobouros and MoH. Overall, these soaps are all the way up there with the very best IMO.