Well volatility is a key thing however security is the most important I believe, for example Binance looks great in terms of security and also volatility as well.
Security of asset and trader is the most vital characteristic of every exchange should have. But for me as a bounty hunter, I often trade on different exchanges given the fact that not all ICO's are going to land on each and every exchange. I dont have preferences on exchanges as long as it is safe to use and secured.