Is there an advantage to THIS cable over the standard AV cable? I already have the component cables - does this one give better sound?
Technically, it should considering it's shielded/grounded (I don't believe the OEM cable is grounded due to a lack of shielding to ground).
I don't understand how any RCA cable couldn't be grounded. It won't work if there isn't signal & ground 
Exactly, RCA/Coax cables function solely on the fact that they're grounded. No ground = no signal.
Some types of cables have additional shielding which serves to protect against external interference. (crosstalk from having many cables bunched together, or near electrical wiring) I'm not positive how they work with regards to RCA, but in the case of shielded ethernet cables, they really do nothing unless connected to shielded connectors, which are grounded. Since Coax/RCA works essentially on the principle that there's sheilding acting as the ground already, selling RCA cables as "Shielded" sounds to me like a marketing ploy, nothing more.
Now, having said that, since it is an analog signal, it's possible that your cables are just a lower gauge, higher quality connectors or made with better quality materials.
Good point about the grounding. The shielding does prevent cross-talk, but the main purpose of shielding in most cables is to decrease signal degradation. In the case of category cables (ethernet) which are shielded, yes they must be combined with shielded connectors, jacks, etc. But (and I know I'm stating the obvious), category cables carry digital signals - not analog. In the case of an analog cable, signal degradation is the biggest factor. So although this is more or less just another marketing gimmick, I also know that OEM cables are not perfect. So when it comes down to it, this cable is a good companion to the component cable for 3 factors:
1) It uses higher quality cable/RCA connectors.
2) It exclude video/s-video (cleaner).
3) It assures the absolute best possible transfer of audio from console to television.
This reminds me of ol' Monster Cable. Lots of extra plastic and some gold plating, zero detectable difference. I remember someone doing a bunch of blind tests with a group of so-called audiophiles and it proving such.
I am almost completely in agreement with this point, but like I said, with so much invested in the component cable, I don't mind having the additional quality in the audio cable (if any).
