Why don't you choose both BNB and ETH?
It is a good investment strategy to diversify your portfolio. Rather than having only BNB or ETH in your portfolio, it is better if you own both of them.
It is even better if you also have Bitcoin in your portfolio too. I mean Bitcoin, Ethereum and BNB are most important cryptocurrencies you should have in your portfolio.
For others, you can choose FTT from FTX exchange, KCS from Kucoin exchanges because so far they are good exchanges and they have been tested enough by the market. In next bull run, their exchange tokens will grow well that is good for your portfolio.
One of the best strategy to invest, hold and earn passive income while dealing with cryptocurrencies is to hold more coins instead of one. ETH and BNB are both on my portfolio, I still have more. If comparing both, they have their own blockchai with different tokens and they are well known, if the next bull run starts, they will both increase. I checked their price and ATH, they both are not that volatile unlike many other altcoins, they both worth buying.