I have used most of the exchanges out there and for me personally the best has been Bittrex. It works well and withdrawals are usually fast but it has some issues like every other exchange out there.
Main thing to watch out with exchanges is the current volume on the coins you are most interested in as it will provide a bigger market to play in and it most likely will give you better rates. There are coins that do better on Bittrex while others are mostly traded on Poloniex so make your decision based on that.
you got this right every exchange favorite one altcoin to be main seen this when LTC gone wild few month back so any exchange is good only is problem what you want