My main exchange was Bittrex before Binance came out, I first tried Binance and then decided to move all my business there. In this business to success, you have to focus on support and that what Binance did, Binance support is really strong and fast and any trader will love this, no one will accept to see his money frozen for many days while losing money because of poor support, and that problem was one major problem on Bitrrex, it didn't happen to me but I see others suffer because of this.
Right now Binance has what it takes from good support to smooth user-friendly UI.