Bitcoin's smart contracts are pretty much limited to multisig transactions, time-locked transactions, and transactions that unlock when given the input text tha

Bitcoin's smart contracts are pretty much limited to multisig transactions, time-locked transactions, and transactions that unlock when given the input text that hashes to a certain value. The only state that Bitcoin transactions can "read" on the blockchain is whether their inputs are spent already (and they read that by failing if their inputs are already spent). Compared to Ethereum, Bitcoin only supports a couple special cases. Ethereum allows arbitrary smart contracts. With Ethereum, you could almost trivially reimplement Namecoin without needing a separately-mined blockchain. You could make a decentralized prediction market (Augur and Gnosis are two projects working on this) out of smart contracts on the Ethereum chain that include systems to reward people who supply correct real-world data to the on-chain Ethereum smart contracts. Both of those use-cases are far beyond the special cases that Bitcoin supports.