Both blogs and wikis have their strengths and weaknesses.
Blogs are more flexible for pleasing visually and offer better page interactions, they are (often) easier to navigate and use in general. On the other hand, storing information in blogs is far from perfect, even though they do provide number of ways to store the information (post and page, categories, tags, etc.)
Wikis are, on the other hand, just perfect repositories. Extremely simple to use, run and maintain, they provide all the necessary ingredients of robust learning repository. Wikipedia is striking example of wiki potential.
Combing these two systems, we get all the benefits from each while losing all the weaknesses! Here is the example: Culturepedia