Al,
There is another way to look at it.
Since technically speaking there is no reason to assume one cable should be any better than another (given your caveats on gauge, properties etc.) then one can conclude that differences are most likely due to the way the equipment behaves. A reasonable engineering "philosophy" is that well designed equipment which is well matched together should be capable of performing perfectly well with any number of acceptable cables. Therefore, if some equipment turns out to be highly dependent or sensitive to a piece of wire than it really might be worth considering to avoid said equipment or its combination in a manner that causes such unreliable performance. (I exclude cables that are designed to be filters or act like an equalizer from these comments - stuff that is deliberately designed to change the sound)
There is another way to look at it.
Since technically speaking there is no reason to assume one cable should be any better than another (given your caveats on gauge, properties etc.) then one can conclude that differences are most likely due to the way the equipment behaves. A reasonable engineering "philosophy" is that well designed equipment which is well matched together should be capable of performing perfectly well with any number of acceptable cables. Therefore, if some equipment turns out to be highly dependent or sensitive to a piece of wire than it really might be worth considering to avoid said equipment or its combination in a manner that causes such unreliable performance. (I exclude cables that are designed to be filters or act like an equalizer from these comments - stuff that is deliberately designed to change the sound)