I've owned both, for extended periods. I loved the look and compact size of the Bling, as well as the clear, sparkling sound.
After some dozens of hours of burn in, the Cotton Dock provided much better sound quality. It was more robust, lucid, extended from bottom to top, greater bass energy, more inner detail, and seemed to be generally more transmissive of musical information. The Cotton Dock was my reference cable. I now have a Jumbo Silk Dock (not currently available) and I feel it's even a bit better. Externally it's the same size as the Cotton Dock, though the conductors are somewhat different, as are all the "Jumbo" cables.
Cotton Dock is a superb interconnect and a very audible step up from the lovely Bling Bling Dock. Be careful not to judge it out of the box. Mine (though it might just have been mine) sounded very veiled (almost muffled) at the start, but cleared up throughout the burn in period (I don't have my notes handy, but it was about a week of intermittent play — so some dozens of hours). Some manufacturers recommend 100 hours for silver conductors, but not all silver cables are the same, so…
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