Frankfurt to Munich or to Amsterdam

It depends on where you want to go and what you want to see and do. No one but you and your family can decide that. Then leave from the closest airport. If you don't have ANY ideas, perhaps start with the Explore Europe section of this site, and the At A Glance sections within each country/city.

What time of year?
If you already have flights booked out of Amsterdam, why change? If it where me, I'd do Rhine Valley, Mosel Valley, Cologne, Amsterdam. More than enough to fill 8 nights.

I'd probably spend four nights in Munich and four in Amsterdam, because I like cities, historical sites, museums, architecture, boats and photography. And I don't like changing hotels. From Frankfurt I'd probably go to Munich first to reduce the amount of time traveling between cities and I'd take the train. Then I'd fly to Amsterdam. I don't like driving, I love trains, and I won't spend fewer than two nights in any hotel.

On the other hand, if I were traveling with my sons the Tank Museum in Munster has long been on their hit list. So: train from Frankfort to Munster, 2 nights, train to Amsterdam, 3 nights, fly to Munich, 3 nights. It all depends on what you want to see and how you like to spend your traveling hours.

With 8 nights I would fly home from Munich and spend that whole week in Germany. Munich has the wonderful historical science museum, the Treasury, the Viktualen Market, great beer halls (for food and music and ambience, not just beer), and a chance to visit Dachau. (Your boys are old enough to have that experience.) They also would enjoy the joyful feeling that Munich gives off. There is lots more, but you can read up on it in an RS or other guidebook. You could spend half your time in Munich itself, and then a few days heading to the Bavarian Alps or Rothenburg and Dinkelsbuhl (sp?). Save Amsterdam for another trip and save the travel expense for going there.

We traveled to Europe with our kids as teenagers and they were interested in many more things than I thought they would be. They were really impressed with the medieval churches and castles and the food.
Whatever you dec ide, enjoy!

If you want to see Bavaria, fly into and out of Munich. Don't go to Frankfurt.

If you want to do the Rhineland, fly into Frankfurt and spend your time visiting the Rhineland and the Black Forest. Visit Cologne, Trier, Mainz, Rudesheim, Heidelberg, Triberg and Strasbourg, France.

If you want to see Amsterdam, you need at least four full days, you could also, visit the countryside with windmills, etc outside Amsterdam and also take in Brugges.

Sam has it right, IMHO.

"We will be traveling with two teens (15 & 18). They both like to visit historical sites."

Here are some worthwhile places in Germany - in between FRA airport and the Netherlands - where you can peek into the past.

MAINZ (on the Rhine, just 25 minutes from FRA airport.) Great place, great for exploring history too:

https://www.tripadvisor.com/Attractions-g187393-Activities-oa0-Mainz_Rhineland_Palatinate.html

UPPER MIDDLE RHINE VALLEY (downstream from Mainz, a UNESCO World Heritage site:
- Old-world villages (Rüdesheim, Bacharach, Oberwesel, Boppard, Braubach)
- Medieval castles (Marksburg in Braubach, Rheinfels in St Goar offer tours.)
- Day cruise past castles, castle ruins, vineyards, etc.
- Outdoor activities (hiking on the Rheinsteig and the Rhine Castle trails, biking as well; chairlifts to trails in Rüdesheim and Boppard)
- Wineries (in most towns)

BAD SOBERNHEIM (not far from Bingen; collection of historic buildings at the Rheinland-Pfalz Open Air Museum from the past 500 years or so lets you see how the locals have lived in this area.)

REMAGEN (north of Koblenz) for its WW II museum (site of the battle for the Bridge at Remagen, as depicted in the 60's movie by that name.)

COLOGNE (further north of Koblenz on the Rhine) for Germany's most-visited landmark (Cologne Cathedral), Roman history, WW II history (Nazi Documentation Center.)

MOSEL RIVER VALLEY (extending to the SE from Koblenz)

• Trier (Ancient Roman History)
• Burg Eltz Castle (near Moselkern)
• Old-World wine villages
• Geierlay Suspension Bridge
• Scenic Hiking and Biking

I might fly into FRA and out of LUXEMBOURG or COLOGNE if all my time were spent in these places (The Dutch often vacation in this area for 1-2 weeks at a time.)

Month of the year? It's a factor.

I prefer Amsterdam to Munich. Are you air tickets really Exchangeable?

But with only 8 nights, I wouldn't necessarily try to visit two countries either. However, have you looked on Goggle Maps yet, before choosing cities? It appears to me that there are trains to Amsterdam that are faster than the trains to Munich! You did not say how may times you want to change hotels or cities during the 8 nights.

Honestly, because of superb daytripping (by train) options, Amsterdam is good for more than week, on a first visit. I agree you can visit Salzburg and maybe Melk from Munich, but it gets tedious after a while to change hotels. We stayed three nights in Salzburg and three nights in Munich.

I'd make the switch. Get a car and do a road trip. There are plenty of "historical sites" between Frankfurt and Munich. Maybe drop the car for the last couple nights in Munich to see the city. Fee for drop-off in the same country will be lower than to drop in a different country. Germany is very accessible for teens, and it's more affordable in nearly every way than Amsterdam (not that flying out of Amsterdam requires you to stay there and break the bank!).

Thank you all for your replies. I have a lot to think about about.

It depends a bit on the airline and where you are flying to.. I fly Delta usually, and there is a much better selection of flights out of AMS. I also have shifted to getting a late morning flight (10:00AM or later) and direct to the US. For Munich, at least for me, there are fewer options, and most are earlier in the morning.

A big plus is also that I seem to be in the Amsterdam area often, a 2-3 times a year recently, so I know where to stay, things I want to do my last day, and transport to the airport is a breeze from almost anywhere in the area.