Two traders place the same limit price, but have different intentions.
The first wants execution as fast as possible and is ready to take the available liquidity.
The second wants his order to first enter the order book as a maker. For this, there is Post-Only: the order must not execute immediately against an already existing order.
The advantage is control over the execution type and maker fees. The trade-off is that the market may move without any trade.
In TradFi Perp, I would choose Post-Only only when it’s more important not to overpay for urgency than to guarantee getting a position right now.
There is no “better” flag. There’s an honest answer to the question: am I providing liquidity or taking it?
The first wants execution as fast as possible and is ready to take the available liquidity.
The second wants his order to first enter the order book as a maker. For this, there is Post-Only: the order must not execute immediately against an already existing order.
The advantage is control over the execution type and maker fees. The trade-off is that the market may move without any trade.
In TradFi Perp, I would choose Post-Only only when it’s more important not to overpay for urgency than to guarantee getting a position right now.
There is no “better” flag. There’s an honest answer to the question: am I providing liquidity or taking it?