Topics Over Categories
If members are visiting a page, they want to learn something new about that topic, see questions they can answer, and perhaps find out who are the rising stars within this field.
This is why categories (which only show a list of discussions) aren’t a great option. It forces members to go elsewhere to find blogs, news etc…
Topics, however, display discussions, content, and leaderboards, in a single place. Members can find anything that’s new without having to visit multiple pages.
In an ideal world, they can also see a separate leaderboard for the top members in that topic.
Topics also allow more flexibility. Not every item of content or discussions your members create neatly falls into a single bucket. If you can add more than one tag to content, it can be displayed in more than one place. On some platforms, members can choose which categories to follow and develop their personal feed of new, relevant, activity on each visit.
Members care far more about the topic than they do about the medium. Make sure they can easily see everything that’s new in a topic in a single place.