For me the most secure exchange is kraken. The best in terms of fees is Coinbase - for withdrawal it is almost 0 fee. The worst exchange without any doubt is Bitstamp. The fee is enourmous 0.005BTC. And each week they send me new emails asking insane things, to prove the origin of my bitcoins, fiat, by sending bank and credit card statements, pool statistics, and many other things. I stopped using this hilarious exchange several months ago.