My two cents: I've used WP and MT a fair bit. The Real Florist Blog we publish here at FC is currently based on WP (used to be b2evo). All the corporate sites and ecommerce sites we publish at RKF use Movable Type (the monthly hosting fee includes Movable Type and an e-commerce shopping cart called SquirrelCart).
MT is available for free for personal use, even before the open source release of version 4.
In the end it comes down to personal preferences between WP and MT, the two leaders in the blogging world. My preference is for MT partly because of the interface being cleaner and easier to navigate, and partly because of the reliability of the plugins developed for it.
Both WP and MT use plugins to expand the features - it's been my experience that while OS platforms allow for great expandability through plugins you're at the mercy of the developer as to when and if they provide updates to the plugin, and if they will support it continually. I've had more bad experiences with Drupal and WP plugins than with MT.
To be fair, even with a commercial app like vBulletin that FlowerChat runs on, sometimes the add-on modules developed don't keep up with the latest version of the app, meaning we have to lose that feature to keep up to date with security patches or take a risk to keep the feature.
Ryan