The obvious answer is Poloniex. Yobit is irrelevant these days when you have huge exchanges (such as Poloniex) dominating the market.
That's true, Yobit doesn't have all the coins and has lower volume, but their support is also working much faster.
For instance, when BCC came out it wasn't added on Polo, only on Yobit and Bittrex, but Bittrex required 20(!) confirmations which used to take 12 hours at the time, while Yobit only 3, which they reduced to 1 a bit later.