Bitfinex is my favorite exchange. They have low trading fees, high trading liquidity and the most important of all, a extremely fast and user friendly customer support. I cannot stress enough how necessary it is for exchanges to have a good customer support and Bitfinex is actually one of the few that offers that. The only down side is that US citizens cannot use the platform, other than that, if you're not a US citizen I highly recommend you to use Bitfinex.