I moved this blog from Wordpress to Movable Type 4 a couple of weeks ago, and I am completely sold. Don't get me wrong, Wordpress is fabulous software. If has a lot going for it:
- It has a large development community producing myriads themes and plug-ins.
- It is cleanly written and easy to customize if you're the coding sort.
- Each and every page is dynamically generated (give or take a cache), so posts and comments appear instantaneously. This is extremely friendly for conversations in the comment threads.
- There is a huge user-base making it very easy to find answers and support online.
- It's offered as a managed install by many hosting companies.
Most of those advantages, however, are a function of popularity. There are lots of people using, supporting, and coding for it. As a result, it's also very commonly targeted by vulnerability scans. It doesn't have the best security record, and older versions of the software are low-hanging fruit.
The dynamic generation of pages has it's drawback as well -- it's resource-intensive. Every time somebody hits a page, the database is queried. I use Dreamhost, which while offering a lot of value for my hosting dollars, doesn't have the fastest servers on the planet, and all those database cycles slow site response down significantly.
This is where Movable Type shines. Instead of dynamically generating pages on request, the pages are written out as flat html whenever the changes are made. This means that the server seems snappy and responsive even on a slower host. The flip side of this is that posting and commenting takes longer since it's writing changes to disk.
While there aren't as many themes out there to download and adapt, the ones that Movable Type ships are slick and very easy to modify (very tight css + a few graphic elements). I haven't found a need to do much to them other than change colors and the banner graphic.
As far as the cleanliness of Movable Type's code base, I have know idea. I haven't needed to customize it at all. The most common reason I have to modify open source projects is for custom authentication schemes, but Moveable Type supports OpenID right out of the box. Unified identity management is a difficult problem to solve, and allowing federated authentication without changing a line of code is a major feature in my mind.
Movable Type also has a very simple and easy to use "template" system that makes tasks such as generating a sitemap very easy. It might be a little steep for a non-technical user, but if you can read or write the most basic of code, there will be almost no learning curve at all.
So, in summary, Wordpress is great software, but I'm sticking with Movable Type for three reasons.
- Speed. It is the fastest load in the game.
- Flexibility. It's OpenID integration and templating system allow me to do almost anything without resorting to rewriting any code.
- Security. It has had only nine medium or severe vulnerabilities in the last five years. Wordpress has had 18 so far this year alone (according to the National Vulnerability Database).
So there you have it, a case for Movable Type by a long time Wordpress user.

I've never been able to get into Movable Type, although trying on several occasions to run a Blog using it. Either way, I like the idea of competition between the two, and with two strong Blogging platforms users of both will benefit as one tries to outdo the other.
Hi Don, welcome to Movable Type! I work with the team, and we're always glad to welcome people to the community. For what it's worth, we agree with all of the points you've raised above -- bloggers are lucky that there are a lot of good options out there for which technology to choose. But more and more, we're hearing the third point you raised there, that security is just not one of the things you want to have to think about when you're trying to share your thoughts and ideas. It reminds me of the bad old days of Windows XP (pre-SP2 or Vista), when it was all Blue Screens of Death or security vulnerabilities, and it was enough to make it feel like too much work just to try to do basic tasks.
At any rate, we can't wait to see what you do with MT going forward, and don't be shy about making requests for what you'd like to see from us as well.