comparison of different dedicated AC line types?

Have no experience with "greenfield" conduit. At one time I did directly wire 12ga. romex to my system power strip, bypassing the duplex - just to see if there was a difference in sound with and without the (regular) duplex. Indeed there was. Much better harmonics and overall sound without. Listened that way for a month or 2, but decided to choose an upgraded duplex due to the fact that if my house burned down for any reason the insurance co. would then have grounds to not honor the claim - even if the missing duplex itself was not found to be the cause of the fire.

But, in general, I've since come to understand that ALL connectors are, sound quality-wise, to be considered the spawn of satan...duplexes, light switches, dimmers, audio and video component connectors, speaker connectors, circuit breakers....wherever a wire is interrupted there is the potential for sound quality loss.

I've run 10 and 12 gauge both romex, Greenfield, and a several others such as THHN wire twisted and pulled through conduit in my eight dedicated outlets. One of my 10 gauge twisted THHN wires were even cryogenically treated in deep submersion.
To be honest I don't notice a difference in sound bassed upon what I described above.
I have tried a number of different high end audiophile outlets, and I do detect changes in sound with them.
I'd suggest you run whatever is the easiest for you that meets your code in your location.

if you won't find anyone done the exact comparison, you can do that on your own hiring electrician and requesting him to provide a couple of different dedicated lines that you're gong to be experimenting with. make sure that he doesn't take you as a nut case tho.

Thanks for your responses. I am capable of running the wiring myself as I was a mechanical contractor.
Thanks to Lak as you have done what I was interested in. I think I will run two different ones to see if I notice any difference in my setup, then go from there.