Firstly it is incredible to me that you have not done the most obvious thing and used your ears. It is so easy. All someone needs to do is take a bundle of cables of various makes and/or models of your choice and then select some CDs or digital files or Vinyl whatever. You do not need an audiophile quality system, a laptop with a good media player installed and a USB cable feeding a DAC from which out comes the analogue cables into your amps AUX1 or line input by any other name. AIMP is by far the best media player for my equipment to produce what sounds best to me - I know that because my ears have told me so. Other media players may be other peoples preference. Various other tweaks come into it like the codec package for the digital files will have choices for LAV or ffdshow or microsoft digital decoders and then I wonder how many people get that far and beyond to untick the dynamic range compressor box which seems to alway come ticked by default, and the other 101 different options. Anyway once all that is sorted plug in a USB2 or USB3 A-B cable of known high audio quality to a DAC with USB in or go via a converter if the DAC doesn't have one. From then on it is a simple case of doing A/B comparisons and listening. Some cables will bring the music forward, others will make it seem to be more distant. Some will make the loud bits louder and the quiet bits quieter to produce a presentation that is exciting and dynamic but lose a lot of the finer detail or quiet bits- assuming the music has any to lose. Other cables will squash the loud bits and so preventing them from dominating and that will bring the finer detail up. Unexciting, undynamic and yet well detailed. Most will be somewhere inbetween but I'm just making a point. If all cables are the same then there would not be a problem with long cable runs. Most of us in domestic surroundings do not have to have long cable runs but live performances do. Imagine how long the cable runs have to be to wire up an orchestra. The longer the run the earlier high frequencies roll off, sheilding has to be better, hum rejection means the cable has to be better engineered. Cables must not run parallel but cross at 90degree axis. The best cable would be no cable at all, the second best cable would be a cable that has no influence over the original sound or recording at all but as all amplified and recorded music starts its life by coming through a cable no-one on earth can know what the original sound is or should be. The worst cables are cables with lots of their own charactor that alter the sound from the original, but again no-one can know which cable is a worst cable and which isn't unless they know what the original unamplified sound sounded like. Music that is electronic from the very start from electrical musical instruments rather than acoustic go through cables right from the start and there is no way ever of knowing which cable was or was not accurate or with too much charactor. But what is clear by now is that all cables are not the same. For sure analogue cables do influence the sound we finally hear but of course that is in combination with all the other equipment that eventually produces the sound coming out of our loudspeakers. Digital cables do influence the sound, even though in theory that can't happen. But to those who can hear a difference, the current belief that a bit entering the cable at one end must come out the other end identical know there must be other things at work that currently is not understood.
As bad as somebody who wont use their ears and wants to believe all cables are the same are those who believe one make and model of cable must be good and another make and model bad just because what hifi says so, pointing to a review rather than plugging some of those apparantly poor cables in and deciding for themselves. Ultimately if someone really wants to believe all cables are the same I expect their brain will override their ears and they will all sound the same.
If for no other reason this huge wadge of text has been good typing practice and the killing of half an hour free time. And cable is a topic some people with interest in hifi love talking about - myself included. Probably because they can be such a low cost upgrade. Gotham GAC 1 analogue interconnects are by far my prefered cable in my system but that doesn't mean I kiss them goodnight and they do come well down my list of lifes priorities.