Keep the BNB and if you're wanting to invest in another altcoin. It's another long term coin that you should hold just like Ethereum. So these two are the long term coins that are being held by many.
Many newbies have been told to buy as much as they can but that's just wrong. They're prone to losses if they'll just bunch of those suggested new projects.
I consider Ethereum a much more reliable investment than BNB. If a person is just starting to form his investment portfolio, then it should consist of fundamental coins, these are ethereum and bitcoin, but since the topic is discussed in the altcoins section, then let it be ethereum. I do not want to say that the BNB is a bad investment, but I still think that it is a much more risky investment, since there are risks of a hacker attack on the exchange, or some kind of problems with the regulator, all this can significantly affect the price of the BNB.