There are many ways in which Arbital makes for a better blogging platform than existing solutions. (By "blogging content" we specifically mean content that's owned by a user or a small group of users and is not publicly editable.) If you've read through all Arbital features, you can probably see why it's the best choice, but here we'll highlight a few key distinctions.
SlateStarCodex has a great post analyzing some of the evidence for Vitamin D efficacy on bone health, cancer, mortality, and the like. Can you come up with a reasonable query, not directly mentioning SSC or the author by name, to find that post on Google? (Make sure to enable "hide private results" option if Google knows you are a SSC fan.) Probably not easily, if at all! This is a common problem with all blog posts: they fade away into obscurity the moment they are gone from the front page, even while they continue to be very relevant.
On Arbital, each blog post is embedded in Arbital web, so it's connected to other pages via tags, links, and other kinds of relationships. This means when a reader browses Vitamin D and cancer topics, they would see SSC's blog post in the "Related" section as long as the post remained relevant. There are some parts of Wikipedia that have been written over a decade ago, and yet are still read by millions of people today because the information is still up-to-date. Arbital can do that for great blog content as well.
The general case is explained thoroughly here, but in the special case of blogs it becomes even more relevant. A blog writer has to make tough assumptions about what the reader knows or doesn't know. Did the reader read all the previous blog posts? Or is this their first one? Do they understand math notations? Do they have enough knowledge in statistics to understand why this critical mistake was made and how to avoid it? If the author assumes the user to be ignorant, they will end up with a very long post that will bore most people. If they assume the user to be highly knowledgeable, they will end up with a short, on-point post that will only be accessible to a tiny minority. Arbital allows them to write the post so it will dynamically change based on user's current knowledge. Furthermore, it allows them to create a whole graph of posts that logically build on each other or on existing Arbital content.
And in case you were wondering: yes, Arbital does have a blog!