Personally for me, I am using Binance, Bittrex and Kucoin at the moment. Certainly my first criterion is good security, they all have that, and most of the time, and the security of your account is usually dependent on you as an individual. Secondly, the trading volume and fees is one thing I really do not joke with and that has made binance and Kucoin my main exchanges that I used.

For some reasons, I guess the only reason I still do some trade on bittrex is the loyalty, but the fee after the feel of binance and Kucoin, can be pretty frustrating for 0.25% and I really wish that can be changed but all the same, it is also a very good and reliable exchange.