[95avblm3]

I did all three: Porsche, Mercedes & BMW 2 years ago... Did them while my wife was at a conference working. I spent a day at all three of them. To me, Mercedes was hands down the best of them. As Rick Lee said above, the Porsche Museum is not all that big... So I did the Porsche factory tour the same day. I think you have to call or email ahead but it was awesome and well worth it.

So my advice is plan a day for each. Maybe you won't spend the whole day there but at least you won't be stressed about missing out on something. Make sure you check which days of the week the museums are closed...