Cannot tell you much cause i've only experience 2 crypto exchange. But i will give you a short review for those exchange. First i used poloniex and its good before it has a chat box for all users which is very unique cause you can know what is happening or what are the thoughts of other investor within the market but the developers remove it eventually. I dont have any issue at all using poloniex but i notice that time that the user of polo are dercreasing so i transfer all of my asset to bittrex and until now i am using it. In Bittrex you can experience the a real trading cause they have a lot of tools and chart indicators that can help to annalyze the market though poloniex also have indicators but in bittrex it has all you need. So i must say these two exchange have a good platform for trading.