Thanks for the video @mjcmt, I find this stuff interesting from a standpoint of how marketing and audiophile lore, i.e., stories told (not around campfires but) around these forums, have shaped opinions and purchases made by "audiophiles" over the years.
I am sitting here with three "audiophile" outlets, or AC receptacles, an older Porter Port, an Acme silver-plated outlet, and the Furutech GTX-D (G). Porter Ports were sold by Albert Porter and consisted of Hubbell outlets that were subjected to a cryogenic process. He originally used the 8300H outlets and later switched to the less expensive 5362W. Acme outlets have expanded to include a variety of styles including a heavy duty model. Common to all Acme outlets are their cryogenic treatment and silver-plated contacts, and a somewhat reasonable price for audiophile stuff.
The purpose of an electrical outlet wrt a home audio system is to provide a connection so that electricity can be conducted from your home wiring to your audio equipment power cord. As with any audio connector, this requires a combination of a strong grip and good conductivity.
The vast majority of these outlets use copper alloy (i.e., brass) contacts to provide the necessary combination of conductivity and strength. The PS Audio Power Port Classic AC Receptacle uses "15 coats of polished nickel over high-purity brass." The relatively lower strength of pure copper simply wouldn’t hold up to repeated plug/unplug cycles. However, the conductivity of brass is only about 27% of the conductivity of the ETP copper wiring in your wall, based on the IASC rating. Yes, there are several types of brass alloys, but even the most conductive is barely above 30% IASC. In addition, the nickel plating used by PS Audio is only about 24% as conductive as copper, vs. the silver plating used by Acme (106%), or even gold at 76% IACS.
One way to look at this situation, which is similar to speaker and IC cables that use less conductive connectors, would be to say the path or area of the connector is much less than that of the intervening copper wiring so the connector should not have as much sonic influence. The audiophile outlook would probably be to say "everything matters", which brings us to the Furutech GTX outlet, which is able to use copper connectors because of a unique spring loading mechanism used to grip the plug blades without requiring repeated strain on the copper contacts themselves.
I found this 2003 article from Stereophile where Art Dudley writes about the PS Audio Power Port Classic AC Receptacle. He concluded:
Is there enough of a performance difference to justify the trouble and expense? All things considered, yes: I heard the Power Port make a small, subtle, yet very real improvement in sonic performance. The difference was consistently audible with a wide variety of products, and I’m hard-pressed to think of another way to improve a hi-fi system for just $50.
So the improvement was "subtle, yet very real." More campfire talk, IMO. I find it hard to believe that Art Dudley could pick out the difference between the PS Audio Power Port and other receptacles that are mostly the same except for the nickel plating (24% of IASC) used in the PS Audio receptacle. I have an easier time believing the Acme receptacle with silver plating and cryo treatment could possibly make a sonic difference as could the Furutech which uses copper base metal for the contacts.
In summary, I agree with @mijostyn, the Hubbell 8300 provides excellent grip of the plug blades, which is one of the two most important jobs of the outlet (grip and conductivity). Only a few receptacles address the conductivity issue such as Furutech (and any others that use copper contacts), or Acme with their silver plating. Making something shiny (i.e., nickel or rhodium) does not make it more conductive. Look at the IASC rating of the metals used in your outlets (and your AC plugs) to assess conductivity. If I were in the market for outlets, I would probably purchase the Hubbell 8300 and be done. If I was willing to pay a little more, I would try Acme’s heavy duty outlet with thick silver plating, and which has been cryogenically treated. If I wanted to spend a lot more, I would use Furutech GTX (G) outlets, which are constructed using copper contacts. However, anything beyond the Hubble 8300 may simply be campfire talk - IMO of course.