I lived in Maple in 2011 so I can really only speak for MWL. It had a really nice cafeteria and was right across from Hilton and Jack Trice which was amazing on gameday. 7 years ago it was pretty much like this:
Maple-Definitely the most quiet of the three. Very few parties. The nicest/cleanest. Strict no alcohol policy. Probably the best for someone who is going to take their education really seriously.
Willow: Combo of Maple/Larch. Had some recent updates to the interior. Best for someone who wants to have a good time, but hit the books at the same time.
Larch- Party central. Very old interior. Looking back they were really gross. Also the most fun. Best for someone looking to beer bong Keystone on a Tuesday night.