Poloniex old and helpful support.
Yes they are old but after they are implementing KYC method, I wouldn't even bother to trade on that exchange anymore because I adore the privacy more than the service itself. It was really pleasure trading at Poloniex, but unfortunately after KYC I did quit on that site.
Binance well... They should work with their down time problems.
Never had any problems on Binance, so Binance I think is the best site to trade so far.