On-time reliability of Thalys trains, 1st class?

I understand your concern because using the Thalys involves at least 3 or 4 trains with associated changes.

You can take the TGV from Est to Mannheim and then a simple 20 minute change onto one ICE ... much easier.

The Thalys to Brussels is reasonably on time most of the time unless something outside its control causes it to be late - like most trains...

The 7:49 direct Thalys does the trip in less than 5 hours.

€14 extra isn't very much for a First seat. Do you want/need the extra legroom or width beyond the already very comfortable second class seats? Do you want what extra attention there may be? Or would you rather buy a nice lunch elsewhere in the trip? I don't know what €14 means to you....

Regarding the spending of €14 to upgrade, you're right, Nigel. How could anyone know what to spend that extra money would mean for me. I am looking for a more comfortable seat with extra leg room on such a long ride. I do see that I cannot pick a forward facing seat which to me is a negative. I'll figure that part out.

Thalys' on-time reliability should be as good as any other train. With 3 direct Paris-Dortmund trains per day, that is the route I'd choose. Comfort class tickets start at €70 and Standard class from €35, with limited seats at those rates. Depending how soon you jump on your available travel date, you'll sometimes see both classes for an even smaller price difference. If you want a single seat not next to anyone, you can request that in Comfort class.

With 3 direct Paris-Dortmund trains per day, that is the route I'd
choose. Comfort class tickets start at €70 and Standard class from
€35, with limited seats at those rates. Depending how soon you jump on
your available travel date, you'll sometimes see both classes for an
even smaller price difference. If you want a single seat not next to
anyone, you can request that in Comfort class.

3 direct trains each day? Wow! That's wonderful. Thank you, Laura. With such a difference in price, I'd choose 2nd class/standard class. How soon from the date of travel can I buy to take advantage of smaller price differences?

I believe it's 4 months out. A bit less right now because they're not posted past the early-June schedule change.