Please, can anyone explain to me why expensive cables are so good? To me a cable is a cable...
Zillions of posts on this topic. As you can see from the above, most of us talk about the physical properties of cables... do they kink up all the time, are they reliable, are the plugs high quality, are they available in the length you want, do they have the option for L and/or straight plugs, etc.
That being said, cables have different capacitance, so they can sound a bit different with passive instruments (mainly in the treble response, especially with longer versions of the cable... e.g. 25 feet, etc.). However, there is very little correlation between capacitance and cost of a cable, so cost is not really a good guide.
I greatly prefer some cables (Klotz, George L, etc.) to others, but it's based on the above physical criteria, not a big difference in tone, etc.

Audio signals by nature are Bi-Directional.