hospital grade or commercial grade receptacles ?

Another pointless battle between those who hear differences and those who don't- which has to depend, I have come to believe, not on differences of hearing but on the resolution and nature of the equipment used. In my case, Wattgates and FIM outlets sound different from one another in easily described ways, and better than stock, by far. No competition, no subtle differences, night and day stuff. In my experience, too, although not with outlets, I don't like the sound of cryo'd components: they tend, consistently, to sound more forward, with less air around images, than stock versions of the same. It's a matter of taste.

In response to Irv,

I'm not saying that physics doesn't matter. And I'm not a scientist-- although I am a professor, and therefore used to thinking skeptically, and demanding proof from myself and from my students in our work in the humanities. And heck if I know why some outlets (and power conditioners, and power cords) sound different. But the fact is, they do (at least through my Audio Research electronics, Vandersteens, and good cabling: your equipment might reveal more or fewer of these differences. Some equipment, including very, very good equipment, doesn't change much when altering peripherals). And not a little, and not subtley. You don't have to be a true believer, or a crank. This is audible, and easily audible, to people who don't care one way or the other (such as my wife). In my case, FIM outlets were too dark sounding for the associated equipment-- a phenomenon many others attest to independantly-- and Wattgates were much clearer and brighter (the same applies). As with so many other things in science, one notices the phenomenon first, and then hopes to find the the underlying mechanism that explains it. Although we try to pretend it isn't, much medical research is based upon this fact.