Personally i will prefer binance than kucoin why because binance has high trading volume and their android app is awesome
And don't forget their 50% discount in every transaction if you use their token to purchase. Well everybody loves discount and this is a good strategy to attract more traders. So isn't it obvious why everybody love binance?
In other way, I also use kucoin but just in some rare moments like when my coin isn't listed in binance.