[bleucamaro]

I've done both... with a one year old.

But I split them up into two days. One day we went to the Porsche Museum, and also to the Zentrum dealership (across the street). The Mercedes Museum was done the same day as the Mercedes factory tour. while you could do both in one day, I think you'd be rushing yourself through the Mercedes Museum, which you really don't want to do. Even if you don't do the Mercedes factory tour, go to the factory delivery center (where the tour meets), its worth checking out the cool stuff there too. And while at the Mercedes museum, walk over to their big dealership and check out the cool cars that we don't get over here. If looking for a place to stay in Stuttgart, I had a great stay at the Steigenberger Graf Zeppelin. Train goes right to the Porsche museum.