What is the advantage of a scoring scale with many levels? In my research I have different ordinal variables with 3 levels of scores. Each score represents the severity of a condition. In other studies I see that the same variables are scored on a scale with 6 levels.
What is the advantage or disadvantage of having a scale with a higher number of levels? Having a scale with more levels would allow to classify the variables with more detail, but how would this affect statistical analyses when testing hypotheses?

Fewer bins means more information loss.
Consider my colleague, who is $50$. He read a report about covid prognoses in people in their $50$s. "Wait...I'm more like someone who is $49$ than someone who is $59$," he protested.
By binning into decades, there was an assumption that the difference between a $50$-year-old and a $59$-year-old would be less than the difference between a $50$-year-old and a $49$-year-old.
Had the prognoses been on five-year intervals (so $50-54$, then $55-59$, etc), there would not have been as much of an objection. Even better than five-year intervals would have been two-year intervals. Even better than two-year intervals would have been each age.
