If there truly is a difference in power cords, why don't audio electronics manufacturers supply a cord of their own choosing? especially for the high end : AR, ML, CJ, Cary, etc... They could have R&D buy a variety of cables and find the "best" sounding one and then arrange a large purchase with a discounted price. This will reduce the cost to the buyer
If they did do this, they could claim that they have tested many cables and "this one" is the best sounding for their gear?
I don't find the argument that different cords will sound differently to different ears in different rooms has any validity. One would need to audition both the gear and the power cord with one's own ears in the dedicated listening environment. Difficult to do. It's either that or hope you can find the best sound on your own.
Why would a high end manufacturer of gear ship a product knowing that it doesn't perform as well as it can? Why leave this decision and extra cost up to the listener?
Nelson Pass's written words on this topic are enlightening. They provide clear insight into his opinion on this matter.
If you can hear differences in cords, then by all means find the one that best suits your ears. It's just money.