More time in Warsaw poland or Cracow poland .

wintersbs that's a tough choice. If you are going to stay within the city in either case (i.e., no day trips) I'd lean to Warsaw. If you want to see a beautiful old town, Krakow. I'd say they are about equal in terms of restaurants, night life, shopping, etc. Warsaw if you are interested in WWII museums, monuments, etc. It will take you half a day to get from one to the other, so maybe not much daytime difference.

If one of those is your city of arrival in Europe, that could factor in to your decision. i.e. the first day is usually a throwaway due to jet lag. I have not been to either but studying Rick's book he seems to favor Krakow by a lot. In fact I think he said Gdansk is his #2 in Poland after Krakow. Another option is to depart midday or later in traveling between one and the other.

Wintersbs: Stan and VS make good points; however, having said that, my recommendation would be to spend the greater amount of time in Krakow. I visited both Warsaw and Krakow this past spring and much preferred Krakow. Warsaw has several good WWII museums but the Schindler Metal Works Factory in Krakow (yes, the one from the movie) was remarkable. I recommend visiting the Wavel Castle and don't forget to visit Leonardo da Vinci's "Lady with an Ermine" that is on display in one of the rooms. I believe there is an additional charge--nominal and well worth it. We thoroughly enjoyed the quaint, pedestrian-only portion of the city center and found many good restaurants.

Although you have visited several concentration camps in Germany, I very strongly recommend that you visit Auschwitz--particularly since you will be in Krakow. I have been to Dachau and Auschwitz--and both were moving experiences. However, Auschwitz portrays the concentration camp reality from the perspective of the victim--a far more visceral, emotional, and for me, meaningful experience than Dachau.

I have been to several death camp memorials and each one is different. I agree with the previous poster that Auschwitz-Birkenau is definitely worth a visit. (I've also visited Mauthausen in Austria and Majdanek in Poland).