Plain and simple - Huobi is much much better. I even like their trading engine more, they're older, more established, and interestingly enough - easier to trust.
Binance is only popular because it got all the Antshares investors from Bittrex and it rode the wave. But with the disaster that IEO-s on their platform have been, if Huobi does a better job, it might overtake the #1 spot.