Well, MATE is a fork of GNOME 2 and Cinnamon is GNOME 3 adapted to look more similar to GNOME 2. So Cinnamon is similar to MATE except built on newer technology and more likely to see updates in the future. It is slightly slower than MATE if you have old hardware but I also find it a lot nicer to use. Honestly, I do not see why anyone would prefer MATE to Cinnamon unless they either have old hardware or are long-time Linux users who are completely used to GNOME 2..
As for your other question, when you select which drive to install it on, assuming there is enough space on your hard drive, there should be an option which says "Install alongside Windows 7" or something along those lines.