Execution quality is often reduced to a single number, but placing an order involves several distinct layers: how the price is sourced, how the order is handled, and how the platform reports the result back to you.
For discretionary traders, consistency matters more than any single fast fill. For automated strategies, predictable behaviour under load matters more still.
The most useful thing a trader can do is measure their own realised cost per trade over time, rather than relying on headline claims.