Since WASM can't create or access JavaScript objects directly, I bet it's still slower. MessagePack (or my preference, CBOR) is still useful and faster than JSO

Since WASM can't create or access JavaScript objects directly, I bet it's still slower. MessagePack (or my preference, CBOR) is still useful and faster than JSON if you need to exchange raw bytes from typed arrays (for JSON you'd need to encode them, e.g. in base64).