These are, or course, two great and well established exchanges. The Kucoin ui seems a bit more straight forward, but I am personally more comfortable and experienced with the Binance ui.

As you have referred yourself on Kucoin, I have referred myself on Binance and receive a nice bonus with each trade .

As for credibility and volume traded, Binance certainly takes the crown. Binance has a much larger user base and its trade volume is ~35-40x that of Kucoin - Binance is currently #2 for trade volume on Coinmarketcap while Kucoin is currently #40.