Not exactly.

Comparing bytes to bytes, witness data is cheaper that OP_RETURN ONLY if the data to inscribe is more than 143 bytes.

source: https://bitcoin.stackexchange.com/questions/122321/when-is-op-return-cheaper-than-op-false-op-if

The process of publishing data is also different, since using witness data requires a "commit and reveal" process:

Transaction Steps:
- Witness data requires 2 steps (Commit + Reveal)
- OP_RETURN requires only one (Direct payload)

Data Visibility:
- Witness data is delayed until the reveal step
- With OP_RETURN is instant upon initial broadcast

Fee Structure
- Witness pays fees on two separate transactions
- OP_RETURN only pays a single transaction fee