A stylus is a mechanical element in the measurement chain. As configurations become longer or more complex, rigidity and mechanical behavior deserve more attention.
Why length matters
Increasing reach changes the mechanical behavior of a stylus assembly. A configuration that is appropriate for an easily accessible surface may not behave the same way when substantially extended.
Stem diameter and material
Stem geometry and material both contribute to rigidity. When clearance permits, a configuration with appropriate stiffness can be preferable to an unnecessarily slender or long assembly.
Think in assemblies
Adapters, extensions, joints and star centers all become part of the mechanical path between the probe and the contact point. Evaluate the complete stack rather than focusing only on the final stylus.
A practical selection principle
Start with the required feature access, then build the shortest and simplest practical configuration that satisfies it. More complex arrangements should be used when the measurement task actually requires them.