Why does tx speed on Starknet Goerli Testnet is slower than ZkSync Rinkeby Testnet?

ZkSync only takes a few seconds, while Starknet can takes up to a few minutes

Is it because: Goerli vs Rinkeby? zk-STARK vs zk-SNARK? ArgentX vs Metamask?

Or is it a backend thing? Does tx speed on testnet represent tx speed on mainnet?