wpmu collection vs buddypress??

Trying to install for classroom site, and trying to figure out if BP or the WPMU plugs that do the same thing is the better way to go?

BP seems to need special themes. Assuming the WPMU plugs can use any theme

Basically I want the students to have their own blogs and then also have some groups and aggregate their posts and comments by class (groups?).. as well as facilitate some fun for the kids.