To deem decentralisation you are to check a number of validators or miners. For example, there are only 21 validators in BNB and there are thousands of miners all around the world in Ethereum. So BNB is centralised and this network can be stopped by its head. On the other hand, Ethereum can't be stopped by Vitalik as it is decentralised.
From your perspective and explanation, it can be concluded that between Ethereum and BNB Ethereum is still very dominant to be liked by everyone, even though BNB will not lose in terms of its use because it has very affordable options in terms of transactions.