That is silly. Directionality of a cable is determined from a few purposely defined characteristics. I hate to say this and sound rude...but the quality control must be lacking if you experience an obvious difference. There is absolutely NO reason why a well designed cable would do this. Now if the plugs are the only difference as you state, then possibly this would be more of a hint as to what may be causing the difference. Still, they would have to be composed of different materials in order to be that obvious. If you use a cable that has no indication of directionality, except for drain wire purposes, it should NOT sound different plugged in either way. I only know of two designers who know how to manipulate this phenomenon. One can be found in a 6moons review (just look for the only award in the cable category), and the other is who specifically designed the cables for my systems.
This makes no sense, but yet....
I've got two pairs of Nordost Blue Heaven rca interconnects, both one-meter. One pair has the current sprung loaded jacks. The other has the older fixed jacks (no spring loading). I had the sprung cables between my CDP and amp and they were unbearibly bright - headache inducing. Switching cables around I put the non-sprung cables in and for some reason they sound a little smoother in the treble. Is it possible for two of the same cable to sound different? Is it possible that the plugs could make a dramatic difference? Or am I imagining things?