It depends on what you want. If you want to run one or a few blogs with a few hits traffic a day and if you don't mind updating the script all the time wordpress is for you.
If you want to have an high traffic established blog then expression engine or movable type would be what you're looking for (or textpattern if support is not that important to you)
If you want to want to control lots of blogs then I would recommend
Blogs Organizer and not wordpress MU, simply because it's designed for webmasters with unlimited blogs and doesn't kill your server... Besides that it's easy to handle and you have real good support...