I appreciate that Cardano has good tech in theory, and does offer advantages over ETH in its current state.
However Cardano is still more of a 'good on paper' type of coin, it hasn't been real-world tested to the extent that ETH has. And I do really rate the ETH devs, too.
I like both coins, but it's extremely premature to suggest that Cardano will 'destroy' ETH, which as well as being a strong project also has a huge first-mover advantage in smart contracts.
Agree. Cardano is still vaporware, considering that it hasn't adopted features for smart contract development and execution. This makes it completely different from Ethereum in many ways. Cardano is just a mere cryptocurrency which doesn't have any utility at all (it's just a speculative cryptocurrency) unlike Ethereum. Of course, the team is focusing on delivering a platform which is stable and secure driven from a scientific philosophy. Its academic approach, could allow dApps to obtain lesser flaws than those within the Ethereum blockchain.
Still, Cardano's development is somewhat slow which prevents it from being one step ahead of Ethereum and other popular alternatives within the mainstream world. Without a working product for smart contracts, we cannot say that Cardano will destroy Ethereum in every way. Even after the implementation of a VM for smart contracts, it'll be far behind Ethereum in terms of development and innovation. Which is why, ETH will be in the lead for many years to come.
Despite these facts, it wouldn't hurt investing into both ETH and ADA for the long term. Since they're among the top cryptocurrencies in market cap, they're prone to survive for a long time. Not to mention, their development teams are dedicated in order to make their respective Blockchains stand the test of time. Within the next bull market, ETH and ADA could very well rise in price exponentially like never before. But be aware, that neither cryptocurrency will destroy each other as each have their respective benefits. Just my opinion