Having smaller channels might be easier to download for individual users over large downloads that would require stable connections. This might be useful where individual users are expected to download channels on their own. Also, smaller channel might make analysis of collected data easier/“more readable”. It also comes down to preference on how you want the content to appear visually. Having each topic as a separate channel would necessitate fewer clicks to see the topic selections.
If you’re considering using the “collections” feature, the main benefit there is for efficiency — since it’s uploading using a single token for all channels in the collection.