Flat channels are simple at first and chaotic at scale. Structured spaces take a little more thought up front but keep a growing community navigable.
When channels are enough
Early on, a handful of channels keeps everything in one view. The risk is that as topics and members multiply, the important conversations get buried.
When to move to spaces
Spaces let you group related topics, apply their own access rules and layouts, and gate premium areas behind a tier. Use them once you need segmentation, access control, or distinct experiences for different member groups.