One of the things users are going to seek from this is the use of usergroup permissions. I am not certain by what you have written if that is a function that will be of use.
Currently there is the Journal modification by Andreas that is fully integrated but has limited functionality and then there is Drupal which is also integrated rather well, but styling it is a +++++. (Especially with what I am doing with it.)
Users are looking for an integrated solution for blogging where they control via permissions who gets what and how that has both style and functionality. I believe one of the mods is currently working on a vBblogs application of sorts. (From this site.)
I myself don't know the benefits of wordpress as I haven't used it yet.