For trading, I prefer to choose BNB because it is clear now that the average BNB holder gives them a lot of profit, and when compared to investing, I would suggest using both of these coins, either BNB or Ethereum, because both are very good coins.
Both are good but if you're always in the Binance to exchange and trade then BNB is preferable to you. It is because they've got incentives to BNB holders that might help you out even if they're just a few for those not that many holders of it.
While for ETH, it's overall, for everyone and whoever wants to hold, you can hold it and both are for long term. So if you like ETH's development hold it and the same for BNB.