I used to use Poloniex a lot and had good experiences with them and liked the platform. The main things that made me switch was they stopped their chat box so you could no longer have real time conversations on the exchange with other customers and secondly I heard that some people were having problems with withdrawals and support.

I decided to switch over to Bitfinex which I liked a lot too and they also had IOTA on that exchange which I wanted to buy. Then they stopped allowing US customers so I had to switch again.

This time I chose Binance. I really like Binance so far because they have a lot of good coins and their platform is good.