For me, I prefer Binance over Kucoin because Binance has more altcoins than Kucoin. I do not care about their interface, I'm interested in quality and transaction fees. Binance did better than Kucoin at that point. So I would choose Binance.
Why selecting on one of them while we can choose booth platform for our trades and they are not far on rankings and service providing since they are so good on their own rights and better to have two or more exchange choices since we might gonna lift up with this since we can do an arbitrage if price differential occur.