PS: I've made a small correction and it may be already answering my question: It's possible that while you occupy more space on the blockchain with BRC20, the witness discount is enough to counter any real space efficiency advantage and thus leading to equal or even less fees.
With tiny size of JSON data, witness discount is negligible compared to various overhead to create an Ordinal inscription. By overhead, i mean 2 TX which usually has multiple input/output.