Accuracy in BLDC speed calculation
Depends on what you want and how you will use the reading. Stable reading or accurate reading. Readings taken over a small arc of revolution will be more representative of what is happening but only over short time spans or arc distances, but result in a less stable reading. Extrapolate that angular speed to the entire rotation can introduce inaccuracy since individual variations over that small angular span are extrapolated and applied to the entire rotation which may not be true, though inertia helps even things out.