I have both BW and SW for my 2 HD800s and IMHO both SW and BW works wonderfully well BUT if you prefer less HF then go for BW. You can't go wrong with it.
I have not tried Copper Venom and from feedbacks in the forum it should sound better than BW, however you need to pay more and have to wait for quite some time before you can get it.
I'm ok with waiting, but I am mainly wondering how much better it is and how flexible it is. The HD800 stock cable is really rigid.