The FM2018-BT200 is worth it if you have a good power rate. The other one not so much!
Why do you say that? It looks to me the B8 is more efficient 50TH/s @ 6.4kWh

Cost/TH is insanely low on the BT200.
But with a March delivery date....no thanks!
Maybe they have an inside scoop of the rumored 7nm chips from Bitfury? Or some other new tech?