Megan,
Since all three of you were history majors, I would definitely choose BERLIN over Munich and not just for historical reasons. Food and accomodations are cheaper in Berlin, which is just an amazing, fascinating, captivating, and exciting city. You will see why.
Historical Berlin is mostly in eastern Berlin, ie, east of the Brandenburg Gate. Go the Resistance Museum, if you don't read German, you can get an audio guide in English, it's on Stauffenbergstrasse within walking distance from the DJH hostel on Kluckstrasse--I know I walked it in July---and definitely see the Reichstag building and the Deutsches Historisches Museum on Unter den Linden with its bilingual explanations.
There is also the anti-war museum (Anti-Kriegsmuseum) in the Wedding district--not really surprising that it is located in that district, given its historical reputation.
What you read about in your historical studies about Berlin, you'll see....Bebelplatz, Wannsee, Unter den Linden, Brandenburg Gate, Karlshorst, Kopenick, Rathaus Schoneberg, Pariser Platz, Hotel Adlon and there is lots more.
Of all my trips to Europe over the years, only once did I skip Berlin... it's just a vibrant place.
"definitely...interested in the historical sights"...
see the Feldherrnhalle in Munich, where Hitler was stopped in his coup attempt. Still the Feldherrnhalle shows the statues of the Bavarian commanders in the war of liberation against Napoleon.
AND, when you are in Berlin, the other must see for historical sights is Potsdam to do as a day trip or two days, not only for the sights but what it traditionally represented.