That's just marketing hype from Cardano, which is the same hype being used to promote Tezos. It's based on the plan to allow Cardano smart contracts to be formally verified. Two other programming languages are being developed for Ethereum that are being formalized by independent teams, and will allow formal verification of smart contracts. e.g. an ERC20 token smart contract implementation is being formally verified by the KEVM project. And a third language is being developed with the aim of doing the same.

Also, Cardano is currently centralized and will be until 2018 at the earliest when further upgrades are made in an attempt to make it decentralized. Meanwhile, Ethereum is already decentralized and work is under way to upgrade it to massively increase its scalability. Ethereum is way ahead and has the critical mass of developer and industry support.