I think that the easiest way to visualze the difference in the cables, if any exists, is to connect both cables to the output of an amplifier, feed the amplifier wide band white of pink noise, terminate each cable into a 8ohm power resistor, and then look at each cable on a multichannel scope. Using the math function on the scope, subtract one signal from the other and then you can see the differences in the signal. The accuracy will be limited by the accuracy of the scope of course.
If you want to eliminate the error of the scope inputs, then sample the outputs from the cables with an op amp in differential mode. Make it so you can short the inputs and null adjust the op amp first, then look at the difference between the cables as a difference signal on a scope.If nothing can be seen within the audio spectrum of human hearing, well that would basically prove that no difference exists for practical purposes.
The problem is that cables don't supply their current to passive and non-reactive loads. They are connected to rather complex and dynamically changing speaker loads. You will never get two speakers with the exact same characteristics, so the audiophiles with golden ears will tell you a non-reactive load is not showing you the difference in the cables.
Perhaps the solution to the latter problem is to set up a test configuration where you record the speaker output in an an-echoic chamber with a sample rate and bit depth beyond needed for even the wildest claims of audiophile hearing, and then a change the cables. Take the two audio recordings and subtract them in an audio editor whilst making sure to get the files aligned perfectly time wise. The resulting waveform will display any differences between the cables.
Audiophiles will always find a way to disbelieve the results just religious people always find a away to reinterpret their holy books or twist words to explain away contradictions.