I dont know how the Cup is in Germany, Only the best play in more than 2 (Maybe 3) cup games in the US, there are just so many computers still involved (sadly)
it is the same, but you could say it also for the most leagues(the majority of leagues are bottom division, where lots of bots participate and most likely miss the PO).
So you think a relegation match garners as much experience for your players as a Playoff game? I do agree that a relegation could give more than a League match as its an important game however I do not feel/think its as much as a Playoff game.
Personally i would rate it even higher then the PO because the chanche of an serious impact on the future of the club is much bigger then in the PO, where only 1 from 8 team promote.