Gold plated are typically better and most likely are plated over copper wire. I think length has to get ridiculous like 100' to be an issue (digital signal carrying cables like HDMI are more length limited). I think composite is one of the least sensitive since all video information is encoded on one channel. Just don't use audio cables unless they are 75 ohm, in which case they're interchangeable (low-end or 'basic' audio cables tend to be high impedance); i.e. some high-end audio cables are better than basic video cables for audio or video.