When a migration is needed, instead of just deleting and re posting the question?

Question

The question https://skeptics.stackexchange.com/questions/19036/do-fish-swarms-show-some-intelligence was asked, and it's a biology question. I wrote a comment "This question belongs on Biology.SE" and then flagged it for migration. The OP also put a comment that they will ask for migration.

Oddthinking then posted a comment:

Closed as off topic. No need for a migration. If you want to post it to Biology.SE, go ahead and cut-and-paste (but check their FAQ - I suspect it is off-topic there too.)

Disregarding the issue of whether the question in on or off topic on Bio.SE. Assuming we have a question that is off-topic here, but on-topic on another site, what are the criterias for a migration, and are there scenarios where a deletion and a reposting on the appropriate site are better than migration?

Answer 1

If a question has no answers and zero (or very few) upvotes, then the effect of the migration is merely copying the text of the title and question. It is easier to have the original poster do that with cut-and-paste than to have a moderator do it.

Why is it easier? Well, it is considered polite for the mods to contact the mods of the destination site, to get permission to send the question over. So it takes a bit of time, and the attention of several mods, for a migration to take place.

If it will preserve a good answer, or upvotes, it is worth it. But if it is just the question text, that's more effort than it is worth.

Why do we bother with that formality? There used to be a culture of throwing "trash" questions over the wall to other sites, and asking permission is a way of avoiding that practice. (I understand Programmers.SE would get particularly targeted with migrated questions that would be immediately closed.) Migration followed by Closure is a path that leaves everyone unhappy.