Proof of Work vs Proof of Stake — Technical Comparison

Security Model Comparison

PoW attack: A 51% attack requires controlling more than 50% of the network's hash rate. For Bitcoin: this requires purchasing and powering more ASIC miners than the rest of the network combined — currently over $10 billion in hardware and $1 billion+/year in electricity. The attack is expensive; the attacker's hardware becomes worthless if Bitcoin's value collapses as a result.

PoS attack: A 33% attack on Ethereum requires staking 33% of all ETH ($30B+ at current prices). A 51% attack requires 51% of all staked ETH. The attack is expensive; if caught, the attacker's stake is slashed (destroyed). The economic incentive is further misaligned: the attacker's staked ETH loses value if Ethereum's value collapses.

Finality Comparison

PoW finality: Probabilistic. The probability of a transaction being reversed decreases with each subsequent block. Six confirmations (Bitcoin: ~60 minutes) is the standard for high-value transactions. Technically reversible with sufficient hash power.

PoS finality: Ethereum's Casper PoS provides "economic finality" — after two checkpoints (~12.8 minutes), reversing a finalized block would require burning at least 33% of all staked ETH. For practical purposes: Ethereum finality is stronger than Bitcoin's probabilistic finality at 6 blocks.

Validator Economics

PoW miners: Revenue from block reward + transaction fees. Significant OPEX (electricity). Capital-intensive hardware investment.

PoS validators: Revenue from block reward + transaction fees. 32 ETH staking requirement. MEV (Maximal Extractable Value) is a significant additional income source.