Google’s John Mueller said in a Google Webmaster Help thread that the canonical tag, used to inform search engines a URL has moved, is slower for Google to pick up on than if they used a 301 redirect.

John explained that Google would first have to crawl and index the first page to understand that there is a canonical tag on the page. Once they crawl it and understand the canonical tag, then they can add to their index that the page has moved.

If you used a 301 redirect, the spider would automatically be redirected from the original page to the new page, so there would be no indexing or crawling of the original page to determine if there is a canonical tag on that page.

This all makes logical sense, but I don’t know if it was stated in black and white yet by Google.

John said:

He also added an important point for those who are doing mass usage of the canonical tag. He said:

So keep that in mind as well. It is not just slower for Google to pick up on but also may really impact your server resources, more so than a 301 redirect or making sure your site structure is solid.

Forum discussion at Google Webmaster Help.