According to Crypto Rover, Bitcoin is often referred to as 'digital gold' due to its perceived store of value and deflationary nature, which makes it attractive for long-term holding. Meanwhile, Ethereum is suggested to be 'digital oil' because of its utility in powering decentralized applications and smart contracts, which are critical for the blockchain ecosystem (source: Crypto Rover). This analogy highlights Bitcoin's role as a store of value and Ethereum's function as a utility provider in the cryptocurrency market.