Is there a difference between a Wiki and a Blog? Which would you be more likely to use?

The differences between a Wiki and a Blog is:
A blog is a closed system where only certain people can add or delete the content to the website. Where wiki is an open system where anyone can edit and add content. The idea behind wiki is that the masses will eventually correct any false information.
There is no way that I would use a wiki, where I definitely would blog.