Nucleus/Blogcms is really Multi-blog (I’ve used it for 2 years), and the core works really well. It’s stable, secure, and has o.k. member management. Some things are less straightforward, and things like Trackback and Fancy URL’s can only be accomplished with plugins.
BlogCMS is actually Nucleus with a lot of plugins preinstalled, some skins, and somewhat integrated.
WP is still singel-blog, so you’d need multiple installs. But there is more functionality included in the core, like TB, nice url’s, metadata options, better user management. Also, the development of WordPress is going at a faster pace at the moment…
