Furutech Nanoflux speaker cables

Seems they come with spade connectors for the amplifier end and banana connections for the speaker end.

Interesting that the OP can hear a difference but does not know which is 'better'.  I accept there may be a real subjective difference, but to be objective, the comparison should be with unamplified live music.  (Amplifiers, loudspeakers and microphones introduce their own distortions).  The direction that sounds more realistic should be counted as the better.

If there is a difference, should there be twice the difference if the cable length is doubled?

I could tell an immediate difference between Kimber cable 12 tc when I went with  Furetech DSS-4.1 with the their top end spades and bananas.  There is an arrow for direction of said cable and I run them like this, doubt I could ever tell a difference in direction but doesn't hurt to use as directed right? 

When there is a difference and it is not immediately clear which is better, simply install it one way and live with it for a couple weeks. Your ears will adapt to that sound. Then reverse and you will be able to discern the qualitative differences.

I use a  couple of vintage MIT cables with their magic boxes on one side. Filter?, I could not say, but the boxes always go at the output. So, back to the previous post.

Given that a sound signal is essentially an Alternating Current of varying frequency (i.e. the electrons are flowing in BOTH directions), I don't see how a cable can possibly be directional. I also understand that this hobby is very much like a religion where its followers believe what they will, and no amount of logic will change that. I simply try to sort out the sensible folks from the delusional and stopped going to church when I was 18. I pretty much read these topics for laughs and to figure out who to ignore.