Does it really matter? Well, it depends on what we would like to use them for and what level we will use them.
Blogs are a great source for concrete information and tend to be chronologically oriented. They provide good tools for public attribution of contribution.
Blogs are used to post interesting finds or questions for students to comment on or to respond to. They probably are more of an opinionated tool, so if you're trying to encourage your students to express their different viewpoints, then a blog would be a good tool.
Read more about at Cockroaches and Ladybugs blog.