Bitcoin and Ethereum can both do one-shot payments with UTXOs, but where they store them is the important nuance. For Bitcoin, UTXOs are part of the chain's state and nodes must keep the entire UTXO set to verify new transactions. Spending a UTXO looks it up in state. This means UTXOs must be quickly accessible and can only be deleted from state when spent. The proposed UTXO implementation for Ethereum is different because UTXOs are not kept in state. When created, they are emitted as an event log into history and assigned an index. For spending, the transaction proves that the UTXO exists in history, and to prevent double spending, the chain keeps a single spent bit for each UTXO index, marking is as spent. Bitcoin optimizes for direct look-ups that need no witness against history. Ethereum optimizes for smaller dynamic state by moving "existence" into history and keeping only the min. information needed to prevent double spending. The motivation to go with that approach (which is similar to what Peter Todd described as "Delayed TXO Commitments" for Bitcoin) is its impact on partial full nodes. A partial stateful node that only keeps a minimal subset of the current state doesn't need to store all UTXOs but only the spent-bit structure. This is minimal state for still being able to trustlessly verify/follow the chain. UTXOs can be implemented in various different designs with different trade-offs. On Ethereum, they can provide a cheap solution for (private) payments, without necessarily requiring UTXOs to interact with contracts. It'd be a feature on top, not a replacement of anything.