Googler, JohnMu, said in a Google Webmaster Help thread that 410 status codes "generally" work faster in getting your content out of Google than a 404 status code.
Google's JohnMu said:
A 410 will generally result in us removing a URL faster from the index.
He does add that although 410s are almost permanent, they are not 100% permanent. John added, "we will generally retry 404s a bit more frequently than 410s, but we will still retry them especially when we find new links to those URLs."
Forum discussion at Google Webmaster Help.