I have both - but I just picked up the Chinese 12k yesterday ($19.99 for the 8x2 at the local Woodcraft store!). I honed up several of my coticule finished blades. I don't know which I prefer but it seems that the edges off of the 12k are very smooth. Honing on it is totally different from the coticule, in my opinion. The 12k feels very hard and glass like. The coticule feels very smooth and buttery under the blade. Might just be me.
I bought the 12k to use after the coticule. I'll have to get back at you with more results.