Puritan PMS 156 vs. Audioquest Niagara 3000

Yep a direct comparison which is helpful....any others? 

A direct comparison...with their gear, in their room (not yours)...seems useful to you, why? On what basis do you think that the difference they hear will somehow transcend those differences in gear, room -- let alone taste, physiology of hearing, etc.

This may seem like a snarky question, but I don't mean it to be. I've wondered about these conditioners before and after reading various posts it occurred to me that there'd be no way for me to know without trying them myself. That's why I wonder why you're hopeful you'll learn something with this question.

Can't you get the two units for an in-home trial?  I'm sure you can get the Niagara; try and find a dealer (Puritan have an increasing US network) willing to let you try one.

As I've posted elsewhere, I found that the PSM 156 bested a Niagara 1000 and an Isotek Sigmas EVO3, among several other units.

I have as I am a dealer of both.  I am not sure I would say that the highs were more aggressive with the Puritan.  Just unconstrained.  Both units reduce the noise floor and corrected some wonky behavior with speakers behaving unlike they should.  I have Wilson Benesch and Vivid speakers and the WBs sounded bright without conditioning and the Vivids warm which is the reverse of what I expected.  

That being said, the AQ did sound a little warmer but that may have been the thunder HC cables.  I think extension gets a bit better when you step up to Tornado or Hurricane.  That being said, you have to use all AQ cables to get the best out of the Niagara.  Puritan allowed for mixing and matching without any issue though the Thunder HC cables led to a warmer sound, even into the Puritan.

That is consistent with what I would expect.  Niagara is best with all AQ cables because of the grounding system.   The Thunder HC cables are very good but not quite at the same level as Hurricane or Tornado.