Create new category or subcategory? what's the diff?

Say that I have one category in my instance, ParentC. I set up a second category, NewC, and a subcategory of ParentC called ChildC.

What are the hardwired/built-in differences between NewC and ChildC in this case? All I’ve been able to suss out from reading and searching:

  1. ChildC and NewC similarly don’t inherit permissions from ParentC
  2. ChildC topics will always have the “flair” for ParentC, but of course NewC topics won’t.

What else? (Or please just point me to where this is covered.)