OK. 841s drain less watts, 100W less but here in EU one 841 its 1.734 EUR with power supply and controller and S9 is 974 USD or 830 EUR. 841 is 900 EUR more that S9. So you can buy 2 S9 for one 841 in EU.
https://www.cryptouniverse.at/shop/avalonminer-841-13th-s-including-psu-and-controller/What is better 13,5 TH/s draining 1200W or for same money 28 TH/s 2600W. I don't know its for 100W worth it!?? Please give me better argument!!

Thank you.
So for 280 TH if I buy 20 s9i with psu I will pay using my coupons 17990 usd, for the same amount of Th I need to buy 21 avalon 841 which will cost me 27520 including psu and 2 controllers,so even if I have 30% failure with the antminers, the price per TH is better from bitmain than from canaan.
In these situations, I'd say, get your money's worth. Honestly, for me, the 841 is cheaper than the S9--after shipping. We have a really Great Canaan distributor here in the U.S.= Blokforge. Also, with June being the month of Bitmain's coupons expiring, you may see another price drop. Canaan lowered prices a couple of weeks ago too, so we
MAY be seeing some new equipment being announced soon. That's just speculation, but it seems to fit the timeline of events pretty well.
I think you're both doing great, by staying ahead of the Difficulty. Thanx for contributing to Kano's Pool!!! Goodluck!!!