COSS is Still runner up. Don’t be fooled by the beta stage at this moment and the site barely holding up now due to all the attention and people trying to get in. This project still has to make the first big jump that KuCoin and Binance already made.
No doubt, if they focus on making their exchange performance better and come up with a roadmap to scale the operations. I've some COSS as well, so here's to hoping it improves :)