I think both are very good networks. Ethereum has great scalability and a growing ecosystem. And Cardano has smooth efficiency and transaction speed. ADA also has very cheap transaction fees at the moment. I think both are tokens I will always use. After Dencun ETH is successful I think Ethereum will become even more developed. So as you said they can both be used for different things, like ETH for Defi and ADA for dApps. But I think Cardano will not be able to replace Ethereum because the ETH ecosystem is already very, very large.