Multiple installations of WPMU vs other ideas

Imagine I have my WPMU website that provides blogs to people and want to have two or more different languages support and different communities based on countries.

For example, a German and a French community, each with its own Home pages, like a de.website.com and fr.website.com.

Now my question, could each of this communities have their own global tags, categories tags and all of that?

Other question, should I do this or opt for a multiple installations of WPMU?