This is mostly based on two observations:

• Even in a city where there's a lot of dance interest there are a lot of people who don't want to dance every week.

• It's better if you know more of the people at a dance.

So let's say you're a person who wants to come occasionally, perhaps once a month. The experience of coming monthly to a weekly dance is ok: you know the regulars, there's some automatic coordination that happens when you and your friends like the same bands and callers, you can explicitly coordinate with your friends. But coming monthly to a monthly dance is much better: you are a regular. The more the dances are differentiated from each other the more people with a monthly appetite will end up attending the same dances each month.

Other advantages:

• It makes it easier to match the number of dances to the overall demand from the community. A weekly dance can't scale up or down easily, while changing the number of monthly dances is natural.

• It increases total demand for dances, by making it more likely that there's an option that's a good fit for any individual dancer.

• If the dances are at different halls then you're more robust against a dance losing their hall.

• It spreads the work of organizing around.

• It allows more experimentation and different booking thresholds.

The main disadvantage I see is that if your community is able to support a large number of weekly dancers, there's something pretty great about how tight a weekly community can be. And the dance skill level will generally be higher.

Other tradeoffs?