fix rigid vs fix rigid/small

I am trying to simulate a single rigid body with less than 20 spherical particles in the rigid body. Which one of the fix rigid or fix rigid/small will be more accurate for this system. I read on the manual page than fix rigid/small assigns the rigid body to the particles closest to com and some other stuff. I couldn’t understand which one is more accurate.

Accuracy is the same. The difference between the two is in parallel efficiency with many rigid objects.
But for a single rigid object fix rigid is the best choice.