From Is SO/SE crosspost accepted?:
Posting the same question on two (or more sites) simultaneously is, while not strictly disallowed, somewhat counter productive. It's a rare question that's on topic on multiple sites. In this case one of the questions should be closed or possibly migrated and merged if it has answers.
Where is the question most on-topic? If you can answer that, flag the post on the other site with the "other" option indicating it's been cross posted and include the link. A moderator can review and migrate if they agree. They can also liaise with the mods on the other site to make sure it gets quickly merged or migrated the other way if necessary.
Here's what I said on Programmer's meta when the more general topic came up:
Reasking the question so that it's tailored to the other site's audience is OK. You'll bring out aspects that the first site missed or you'll be able to focus your question as a result of the answers on the first site.
Just copy/pasting the question from one site to another isn't going to work well. It's either going to be totally off message (note not necessarily off topic, but just not "right" for the site) for one site or the other or worse, fall between the two sites and be a bad question on both.
The thing to to do is think about the target audience of the site and think about what sort of answers you want to get.
