I have tried bittrex, hitbtc, cryptopia, coinexchange.io. Now my favorite is hitbtc. in hitbtc you can earn more profit than others because hitbtc limit decimal in certain coin. you can't trade with different one point. for example offer 0.0007100  ask 0.007300. in other eaxhangers not limit the decimal. 0.00712 offer and 0.00715 ask. From the limitation of decimal trading in hitbtc is more profitable than other exchangers. The highest volume trading is btc, eth , bcc, ltc and few other coins.