Fussen to Salzburg - by car

Depends on if you're in the mood to drive through or stop along the way. I would stop at lake Chiemsee, and take the boat out to the Ludwig castle. Going north of Munich is out of the way, but you could stop at Dachau Concentration Camp. It is worth a couple hours of your time. Drive wise it's shortest to go down toward insbruck then cut up to germany at insbruck then across Germany then cut down into Austria once you get near Salzburg. That is almost all highway driving.

Munich is much more interesting and has a lot more to offer than Innsbruck in my opinion, but it’s out of the way for your route. The most direct way for you to travel is via the A12 through Innsbruck. You’ll eventually change to the A8 and head east to Salzburg. Regardless of whether you go to Munich or through Innsbruck, you’ll need to purchase the toll sticker (vignette) to use the Austrian Autobahn…buy at any gas station…7-8 Euros good for 10 days. The A8 is pretty busy right around Munich, but traffic thins out the further east you drive. I seem to recall that you cannot drive into the old city center in Salzburg (or at least it’s really difficult), but there are parking facilities within a five minute walk.

Thanks for the great, insightful and helpful replies!

Oh and one other note. Gas is 20 cents less a liter in Austria than in Germany. Just something to consider while filling up on your trip.

If you're looking to pass through quickly, then definitely Innsbruk. If you're looking to spend a few days somewhere, then I'd vote Munich. I couldn't tell from your question if this was a pass through situation or stay a few days along the way. I thought the Innsbruk area is also more scenic on the way to Salzburg.

Just returned from this area and I would agree that driving though Munich would not be quick. Also, the Vignette cost 7.50 Euro and it's good for 10 days. Gas was cheaper in Austria. Have a good navigator too to simplify your driving.

Also, get a good map and avoid the autobahn too if you're looking for a more interesting drive. We had a great time driving off "the beaten path" and on many side roads, but we factored this into our time, and it did take a fair amount of extra time, but was well worth it. You see some wonderful scenery and towns.