WordPress MU

I have three sites and I need WP on all three. I can't decide between WP and WPMU. I would appreciate if you look at my requirements for each site and tell me what would work better for me on each site.

On all 3 sites i need more than one account.

Site 1 - This is my wiife's site. She is a collage teacher and i already installed it for her students to post their projects and portfolios. The posted materials can't be public nor student names. There are two classes and each class should see only their class projects. The students should be prevented to post to the other class. I worked this around somehow with use of WP and plugin called category access. It's working Ok except everybody can see title of the post but don't have access to it if not from that class. Everyone can post at 'uncategorized' and that is not good because they can put their portfolios by mistake there.

Site 2 - It's like geneaology site/portal. I'd like to allowed some families to have their own page so they can introduce themselves but would still like to have control on it.

Site 3 - My personal site. Requirements same as site 2 but in addition would like to have additional blogs to be private, visible only for certain users with accounts i create for them.

If this is clear to you please help me to decide what to install WP or WPMU.

For only 3 accounts, MU is way overkill.

MU is server level software, not "site level" software like WP.

It's made for hundreds, thousands, tens of thousands, hundreds of thousands and more blogs.

Search for more info. This gets asked a lot.

Site 1 has around 50 accounts.
Site 2 will have several accounts and site 3 only few.

Blogs/ sites is what's important. Not individual accounts. I'd lean towards regular WP as well.

Sorry, my terminology was wrong:

Site 1 has several blogs for now but will have around 50.
Site 2 will have several blogs and site 3 only few.

So for site 1 you want to switch so students have their own blog instead of posting to a specific category in the one blog you have now? If sol, then MU.

The others I'd still use the regular WP.

I would recommend looking at a learning management system like Atutor for site 1 and regulat WP for sites 2 and 3.

Steve

Thank you all for your help. I'll go with MU for Site 1 as andrea_r recomends and WP for sites 2 and 3. I looked into Atutor and it's not for us.