Ethereum's approach involves on-chain execution of smart contracts & applications, which still lead to network congestion & high fees during periods of high demand.

Drivechain's architecture facilitates scalability by offloading complex & resource-intensive operations to sidechains. Ain’t only reduces congestion on the mainchain but also allows for greater efficiency in executing various functions.

The proof-of-work security of the main Bitcoin chain further strengthens Drivechain's security guarantees, making it a robust solution for both scalability & decentralization.