Proof of Work (PoW) and Proof of Stake (PoS) are two blockchain consensus mechanisms. PoW requires miners to solve complex problems using significant computational power, leading to high energy consumption but offering robust security. PoS selects validators based on the coins they stake, consuming less energy and potentially offering greater decentralization. PoW is favored for its security, while PoS is preferred for efficiency and scalability. Each has distinct advantages depending on the blockchain's needs.