BNB is easily the best exchange dedicated action on the market right now and the best altcoin behind only ethereum, the reason ethereum is still rated higher in my books is because ethereum has a longer and stronger track record and with the ETH V2  to be launched soon. I believe the issues of slow and expensive transactions will be tackled.
BNB Blockchain is having great reviews with the fast speed and low transaction costs, however, time will tell if this can be maintained when more projects get on the blockchain