Xeon Phi. Hands down no contest. The 7210 gets 2800 H/s CryptoNight at around 250W at the wall. I am planning on leading a group buy in the near future for about $1250 per, with these particulars:

- You own the CPU and the board, and I am legally bound to ship on demand. You will be issued an ETH20 token as proof of ownership, so ownership may be easily transferred.

- I will provide internet, power, cooling, electricity, and administration for the first 12 months for free. You just give me an address.

- After 12 months there will be a service fee, but a smart contract will limit my profit.

I'm pretty damn sure you won't find a better CPU, or a better deal, for that matter, unless you make your own GPU farm.

Sorry for the digression, but it seemed relevant.