No full collateral needed. XClaim needs vaults (or banks) to lock collateral to the amount of backed value transferred through the bridge in order to punish misbehaving vaults. Because of the opportunity cost of locked capital, this would lead to higher fees for using such a bridge. In substraTEE-bridge, SGX guarantees for integrity of computation. Therefore there is no need for full collateralization.
No relay-contract with on-chain registry of block headers needed. Block headers are stored in the enclave's sealed storage. Less onchain storage is needed on the issuing chain.
Less transactions needed as there is no need for a collateralized issue commitment.