Hyperledger Sawtooth blockchain supports both public and permissioned blockchain implementation, while Hyperledger Fabric only provides permissioned blockchain implementation.
Hyperledger Sawtooth uses the Proof of Elapsed Time mechanism; on the other hand, Hyperledger Fabric uses the Kafka consensus algorithm. Unlike Hyperledger Fabric, Sawtooth supports Seth project, which means Ethereum based smart contracts can be migrated to the Sawtooth platform seamlessly.
In a Hyperledger Sawtooth platform, either all the transactions are processed simultaneously or not at all processed. On the other hand, transactions are executed in batches of Kafka blocks in a Hyperledger Fabric platform.