Berlin – NRW (Düsseldorf) BAB or Landstrasse?

Hello all, I have only had the A-Schein since November 2012, but have already driven almost 3000km in the city and sometimes short day trips. Now I have to from Berlin to Düsseldorf to load there on the car train to Narbonne. From Hamburg unfortunately no more places left. What do you recommend to take a regular day holiday and drive the country roads from Berlin to Düsseldorf relaxed, or to bring BAB and in 5-7 hours the whole thing behind me? Man can stop with the weather in Deutschand this year never be safe. So if rain, then then rather highway.