An advantage of the blog approach to web writing versus the wiki approach
You can argue that in many ways it is basically a tossup between the blog approach and the wiki approach to writing for the web and that you might as well use whichever one you want to adopt, whichever one fits your particular style of producing content. (Given real blog usability you can certainly argue that a blog's chronological ordering is unimportant and a wiki's greater internal links are highly useful.)
However, the blog approach does have at least one significant advantage over the wiki approach: blogs have figured out much better ways for people to keep track of a stream of new information than wikis have. With blogs, every significant addition of information is a new entry and a standalone entity; it appears at the top of a page if you want to visit directly, it shows up as a complete, readable entity in syndication feeds, and you can announce it on Twitter, Facebook, and other social networking sites of your choice.
Wikis, well, have not figured this out, not anywhere near as well. As Aristotle Pagaltzis noted in a comment here, most wikis do not have good support for showing people important changes in a useful way (in syndication feeds or in the wiki itself). I think that this is partly an inherently hard problem. When there is a change, you don't want to see just it, you want to know what it means, and extracting that semi-semantic information from raw text is inherently very hard. With blogs, people generally pre-extract that information for you because they're writing a new entry.
(It doesn't always work even in blogs, because a new entry can be so densely laden with references to other things that you have to follow a lot of links to actually understand it. But at least you have a good chance, especially if you've been following the blog for a while.)
PS: as noted before, this is a difference in the approach, not necessarily in the storage engine. You can write with the blog approach using a wiki engine, and if you try hard you can probably do the reverse as well.