Recently the Swiss Super League was expanded from 10 teams to 12. I think this is a good thing for Swiss football because the quality of the 12-14 best teams in the country allows it. 10 teams was a bit too restrictive for the football development of the players in teams caught in the bottleneck of the second division.
To contrast it with the Premier League which has 20 teams, it would be disastrous for English football to have a 12 team top division. But with the quality of the teams coming up recently and then immediately being relegated maybe 18 teams would strike a better balance?
The overall and average quality of the football matters when deciding how many teams to have in your top division and there's a balance you have to strike. As well as the difference between the top, middle and bottom of the table.
I'd argue that the Bundesliga has seen the benefits of an 18 team league over a 20 team league (shorter season, less matches and less of a gap between top and bottom).
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