I would choose both. Because investing is never investing in any coin or business. it all divides risk. Although ETH is getting better news about Ethereum 2.0 and PoS coming to ethereum. but I still buy BNB because it's also one of the largest and best exchanges I've ever seen. They work professionally and burn more and more coins than before. That shows their sales are increasing and they will definitely break out the old ATH soon.
Both coins have the potential to change the world by storm. While BNB is centralized, it serves a unique purpose in the mainstream world. Binance's cryptocurrency offering could prove to be quite attractive for businesses and companies looking to launch their own securities on a Blockchain ledger that's regulatory-compliant. On the other hand, ETH could prove to be quite attractive for the average investor, developer, and individual due to its decentralized design. In Ethereum, anyone can interact with tokens or dApps, support the Blockchain ledger at will, and do other sorts of things. The trade-off would be scalability, but if ETH stays decentralized, nothing else matters.
People often tend to trust ETH more than BNB, because it's been on the crypto space for a very long time. There's an established branding/mainstream recognition with Ethereum, just like it's the case with Bitcoin today. Binance Chain is still starting to blossom with a very limited number of supporters behind it. It could take quite some time before people will be able to trust BNB more thoroughly. The token has been used for long in the Binance exchange for trading discounts and other perks. Most people have heard about BNB, but they're not aware of that it’s like Ethereum. Maybe it could be lack of marketing/promotion from Binance's side. With the ample resources Binance has, BNB could become one of the greatest blockchains the world has ever seen.
Nonetheless, ETH is and will always be the most trusted cryptocurrency (besides Bitcoin) no matter what. BNB could simply complement ETH in case it becomes clogged by large transaction volume. Depending on our needs, will be the Blockchain network to use. We cannot rely on decentralization for everything, the same way we cannot rely on centralization for everything. It's expected that both BNB and ETH will survive alongside each other for many years to come. Just my thoughts