Ethereum is still the best smart contract platform. It is the biggest smart contract platform to date. Ethereum smart contracts are coded in solidity, a language suitable for smart contracts.
Ethereum has the "code is law" approach to smart contracts. That means, contracts are locked after they are written. They can't be changed. The only way a smart contract could be changed is a hard fork which is very unlikely to happen.
This provides better decentralization and cryptography secures the tokens. But it has its demerits which is, if a bug is found in the code. It can't be fixed and the developers would have to abandon their tokens and fork it on a new smart contract.