I will choice Huobi. Cause, In addition to the basic trading interface (huobi-pro), Huobi offers two trading platforms: HADAX, OTC. Huobi also offers margin trading. It can be seen as an all-in-one trading platform. Of course, huobi still has disadvantages (was hacked in the past, high fee..) but with what they have and are achieving personally I would rate the huobi as the best exchange in 2018.