Prague or Budapest

With just two extra days I would stay in Austria. Two days including transportation is too little for Prague or Budapest.

If you are in Vienna, maybe Brno for a couple of days. A bit farther is Budapest - I think it's about 3 hours train ride. Prague is more like 5 hours on the train.

As you are closer to Budapest that is where I would go. I have been to both a few times and really love both cities, however the food in Budapest puts it a slight bit ahead of Prague for me. Either is a wonderful city, and a nice addition to Vienna, or wherever you are in Austria.

Christine,
We just returned from a trip that included 2 days in Prague,2 in Budapest and 2 in Vienna. Prague without a doubt was the best of the lot. Budapest is big and sprawling. The smog was terrible. Vienna I think does not give you a true sense of Austria. I would go to Salzburg or the lake region with the extra days. But between the 2 listed, Prague by all means.

Austria is so big and so complex that I cannot imagine wasting 2 days in travel. If you are in Vienna, go to Linz or to Mauthausen Concentration camp. we were in the area last summer, and were in the salzburg area. There was so much to do out in the country that we never got to Salzburg at all. Don't waste time on a 2-day trip somewhere - look where you are. There is certainly 2 days of of something to do.