Multiple Authors – Multisite or Roles/Capabilities?

Am looking for advice/opinions on the following scenario.

I have a wordpress website, on which multiple blogs will appear as separate pages (along with a whole stack of static pages).

At the moment, I create the separate pages all out of the same blog, using “category” as the differentiator for each separate “blog” page. For example, there is a “news” page showing only posts of the ‘news’ category; and an “articles” page showing only posts of the ‘articles’ category.

Each category has a different set of authors. The only hassle is I have to rely on authors picking the correct “category” when they post. I could live with this if I could moderate the posts (ie approve them before publishing), but it seems I can only do that if I set the user’s role to “contributor”. But at that role level they can’t upload pictures. If I set their role to “author”, they can upload pictures, but can also publish straight away.

I have looked into multisite (and have a theme “striking” that supports multisites) and a shared host (bluehost) which seems to support multisites), but don’t know if going down that track will introduce a lot of complexity to solve a problem which may be solved more simply by another means.

Thoughts appreciated.