Binance all the way for me. I just checked coinmarketcap and Binance is on the top of the list as far as 24 hours trading volume:
1. Binance
33. Kucoin
If you are just basing everything on UI alone, then its not a good gauge in my opinion.
For me, Kucoin have considerable fees for trading and they also got the fast confirmation of withdrawals and deposits. It's admit-able that binance is far way a better exchange but Kucoin can keep up with other exchanges in terms of fees and volume, Binance is just really the number 1