I think both are worth investing and I am holding both of them but both are different networks, BNB has attracted huge investment during the past one year and it will continue attracting new project as being best alternative of Ethereum with much lower cost. Ethereum 2.0 is going to be fully implemented in the next few months which hopefully will reduce transaction fee significantly.
Tomorrow the London hard fork will run and it's part of the Ethereum 2.0 implementation to be even better than the previous one although in the past Ethereum wasn't even worth calling it bad just because there are others that are cheaper so let's see together how it's implemented run.
Those who are still talking about transaction fee reductions because of the Ethereum 2.0 implementation still seem to ignore what Vitalik Buterin repeatedly says and said: The London hard fork is not going to change the transaction fees. It will stay high during busy times for quite a while. The transaction fee solutions are still quite a bit away.