along the line of the red "mark"
ive owned a base model of sennheiser for 2yrs, cost me $89 au from jbhifi. its been ripped out of my ears countless times and been through the wash about 5 times, its been squashed, stretched and dropped. and it still works... oh yeah its original. recently the cable tore and pulled away from the driver and also from the join seperating the two drivers, low and behold. one of the wires is RED. quite a thick wire to. still works
but i thought id upgrade, and to save money i used ebay (stupid me)
i got this pair of ie7, thought they were the bees knees. didnt sound to bad, good packaging, anyway a week later the drivers fell out of top pocket and into a drain. slight tug later and the cable snapped (at the join) had a look, hmm no red cable. FAKE.
so yes there is a quality difference in cable between the real macoy and a fake. the red cable is much thicker and stronger which will provides a few benefits
1. durability
2. better solder connections
3. less signal loss through length of cable
4. kinking less of an issue, and disrupts signal less (electrical pulses "DO NOT" like traveling around sharp corners...)
hope this sorts your battle of the cables.
cheap is good. genuine is better, and will save you $$$ in the long run