I think that it is better to switch to ETH today, it will continue to grow 100%. But the growth rate of bnb is a mystery. I think this is a good decision.
Why can't have both the coins?
ETH is definitely the no.2 crypto-currency in every aspect. The number of users and trade volumes can give competition to those of Bitcoin at any point. BNB is a relatively new currency, and it is tied to the cryptocurrency exchange Binance. Because of its relation with Binance, BNB does not have the kind of freedom that ETH possess.