I don't think you can tell any difference between the cable lengths as mentioned but adding a 2nd run may very well change what you hear.
Back in the "old days" I used to double up on zip cord & could hear a definite difference between that & a single run, which was especially noticeable in the bass.
I currently have a 5' & 9' section of spkr. cable & can't hear anything unusual. I shortened a 10' pair to change the ends & for a better fit.
The only thing about uneven lengths is they are harder to sell but you can always sell as a single cable.
Back in the "old days" I used to double up on zip cord & could hear a definite difference between that & a single run, which was especially noticeable in the bass.
I currently have a 5' & 9' section of spkr. cable & can't hear anything unusual. I shortened a 10' pair to change the ends & for a better fit.
The only thing about uneven lengths is they are harder to sell but you can always sell as a single cable.