There is a school of thought that says any suitably thick bell wire (2 core) will do the job. So a 2 core 5 amp mains flex will work for example.
There is also a school of thought that says that all speaker cables sound the same.
However (as a generalisation due to the length of the speaker cable) the cable does have elctrical properties - it has a certain resistance, capacitance and inductance. These properties can be influenced relative to each other by the design of the cable and this can potentially have an audible effect on the sound you hear.
So your friend is not wrong in that if he likes the sound then that's great as it works for him. Of course that's not so say that you'll like the sound in your set-up so you might want to try something else.
NAD 515BEE, NAD C325BEE, KEF IQ5SE's, Silver anniversary XT, Chord Crimson interconnects.
Panasonic TX32-LZD80 and DMR-EX77EB