I will be traveling to Prague, Vienna, Munich and Berlin this summer. I need to spend an extra day in either Munich or Berlin. Any suggestions which city would be better to stay in for an extra day? I will be traveling with my wife, son 15 y/o and daughter 14y/o.
Ah, you're opening that can of worms. "Dallas or Houston?" "Paris or London?" "Vienna or Prague or Budapest?" Well, "Munich or Berlin?" is another one of those. I strongly preferred Berlin, but that's just me. Here's a thread with my opinions, along with some others: http://www.ricksteves.com/graffiti/helpline/index.cfm/rurl/topic/91823/berlin-vs-munich-cagefight.html. And here's my trip report for Berlin (and Dresden): http://tinyurl.com/9woj9zo I will say that if anyone in your group is at all interested in science museums, Munich's Deutsches Museum is superb, and reason enough to favor that city. If anyone in your group has any interest in 20th Century history, Berlin wins hands down. Otherwise, you and your kids can look at books and videos (Rick's are on Hulu and YouTube) and, in the event of a tie, flip a coin.
Since you are going to both, and are simply asking which one would be better for an extra day, I will say Berlin, hands down. There is such a variety of things to see and do there. The Deutsches Museum in Munich is indeed wonderful, but one can only spend so much time in a museum.
Munich has something in common with Prague and Vienna, Berlin is quite different. So go for Berlin.
Of course, you could also use the extra day to see Dresden between Prague and Berlin.
How many days are you staying in each? If you already plan on 3 or 4 in Berlin, then I would recommend Dresden as well. If you are only in Munich 1 day, then I would suggest another in Munich. Without your complete schedule, it really is hard to make suggestions. I did a Munich, Prague, Dresden, Berlin trip last year and had a fantastic time! Enjoy your trip!