The difference between a wiki article and a blog are quite different.
First of all a blog gives more context and more freedom for self-expression. You have the opportunity for a better narrative. You are able to place your choices in context, and inform about the sources of your information and other alternatives that you tried and possibly rejected. Blogs have dates if it was something done years ago then it may not be very current. All these things are obvious. Blogs tell you who is doing what, when they are doing it and how well they are succeeding.
See how sometimes the wiki displays totally out of date information. The articles are not attributed. A single page may have about 10 different contributors and may contain outdated information which is over 10 years old. It is not obvious who wrote what and when it was written, or who deleted or edited something written by another. Some of the contributors may have not been involved with Lazarus for a long time, and you don't know if you can contact them to discuss or clear up some issues about the code. Blogs make you know that there is a living community involved with the software you are using.
If you know nothing about Lazarus a blog roll or aggregator will tell you about what is happening with Lazarus. It is important for people who nothing about Lazarus and may be interested in trying it.
And I said earlier, wiki it, github it, but blog it first, ie tell us more about what you were doing and how you came to do it in the way you did and you discoveries along the way. It may be basic or trivial, but someone even less knowledgeable will learn something from it.
IMO it's best to put things on the wiki in order to centralize information. The wiki contains tutorials as well as documentation etc.
I see no reason to blog about it on some external site.
To each his own.