I did a comparison between the Puritan and Shunyata, both the power conditioners and power cables. For the Puritan it was the 156 conditioner and their top of the line ultra power cord. For Shunyata, I tried both the Denali and the Everest and the Sigma and Omega power cord. Of course, price wise, this is not a fair comparison. But, I wanted the best or close to the best for each brand.
The Puritan 156+ultra cord is good, very good, better than the Nordost QB8 (version I) that it replaced. Cleaner, more articulate, more sound stage, etc.
BUT, the Shunyata is simply exponentially better. The Denali is superb, the Everest is appropriately named being subjectively about 20% better than the Denali. In terms of power cords, the Sigma (compared to the Puritan and a Nordost Valhalla) was more articulate, cleaner, provided a tighter, more controlled and substantial bass. Tonal qualities were nearly perfect (classical and jazz ). The Nordost was veiled, misty, clouded in comparison, the music not as present or engaging. The Puritan was not veiled, but "flat" compared to the Shuynata (this does not imply that the Shunyata is colored, it just seems to let more of the music through). The Omega again was about 15 - 20% better than the Denali.
Note: If you are using either the Denali or Everest, you want the XC power cord. If you want to connect just one or two devices so you really don't need a distributor, try the Shunyata Omega QR or QS which provide in the cord the equivalent of the Denali or Everest.
I did this comparison on two systems:
Dealers: boulder pre and amp with Wilson Alexia speakers, Rossini Dac
Mine: ARC Ref6SE preamp, Rogue Audio Apollo Dark monos, Rossini Dac and AMG Viella turntable with SoundSmith strain gauge.