[DominikPeters]

I agree that the booking experience of the DB-SNCF cooperation trains sucks from the DB end, but the underlying blame arguably lies with SNCF which insists on compulsory reservations which is against the philosophy of trains in Germany. On the other hand, in my experience DB offers cheaper tickets for these cooperation trains, most of the time.

But these trains are a special case; in other cases DB is clearly far more pleasant.

[weinzierl]

This is not primarily a problem of the cooperation trains, I have the same situation with trains within Germany. DB-Navigator only tells you if a train is bookable right at the end, right before payment. Before that, it might show "there is high demand", but this is rather useless, especially when you have a school kid and want to book a train a the beginning or end of school holidays, when every train is in high demand. Your only chance with DB-Navigator is to play the whack-a-mole game where you run all the steps repeatedly until the very last step until you find a train you actually can book.

In the SNCF app I have this information right away, that is what makes the difference for me.