Driving from Amsterdam to the Black Forest - A61 or A3?

So you are going to drive through the most densely populated part of Europe at 120 kph? There may be a few lorries along the way to slow you down. Wait a minute, how about totally chock full of lorries, with under powered engines. Look up the German word "Staus".
On the other hand a train will get you there maybe a bit quicker. It goes 360 kph between Cologne and Frankfurt.
There is direct ICE from Amsterdam to Karlsruhe in 5 hours, Freiburg in 6. Leaves Amsterdam at 8:05. Rent a car when you get to one of those cities.

You have the choice between Scylla and Charybdis. A61 is crowded with Dutch trucks, A3 with trucks and cars from everywhere. You will bee very lucky if you can do that 500 km within 5 hours (bare driving time).

Viamichelin does give the nod to the A61, estimating 5 hours 50 minutes doing the speed limit to Karlsruhe, and assuming no traffic jams.

Who knows on the day? Use the Stau Mobil, or whatever you use in the Netherlands, to see the conditions on the day.

A61 is winding and hilly but misses most conurbations, so if you don't get trucks passing trucks uphill at 1 kph speed difference (hah, when didn't that happen?) it might have the edge. On the other hand it has plenty of long high bridges with 80 kph limits and the trucks really do slow it down.

You seem to like the A3. But it is in or near urban areas a lot more and has lots more restricted speeds.

You pays your money and takes your chance.

Then again, you are somewhat vague about the bit of Black Forest you are trying to get to. If you think the A3 and A6 are bad, wait until you have a go at the A5. Take sandwiches.

Thanks for the helpful replies. I am headed to Menzenschwand. There was a fair bit of construction on the A3 in July and a fair bit of traffic in some areas. On the other hand there were a good number of stretches where my Audi rental car could open up and gain some time. I made the run from Amsterdam to Munich in 8 hours including breaks.

If the A61 is going to be filled with lorries passing each other going uphill on two lanes, I'll probably go crazy. ;)

I drove either route every few weeks back and forth to Belgium for four years, so here's my experience... Despite going by more urban areas and seeing more traffic, if everything falls into place, A3 is usually a little quicker. Not by a whole lot, though.

Also, my end-point in Germany was just south of Darmstadt, not all the way to the Black Forest, so the stretches of both roads further south could change the math.

And as Nigel wrote, A5 can get rather Stau-prone, starting at Karlsruhe and continuing most of the distance to Basel.

Vielen Dank Alle.