Yes, absolutely right, both ways got pros and cons! Sure we should not call it 'node' that would be a copy. But what about 'knot'?
I rather meant to see the word "topic" in a different light.
Another idea concerning the optical separation of various 'stories' into news and blog postings would be to use different storytext.thtml files like blog_storytext.thtml news_storytext.thtml etc. It would be much easier to do that then use a whole different theme or CSS file.
This feature would be good anyway especially if a site becomes bigger and you have some sort of subdirectories and you definitely want them to look different.