In a Google Webmaster Help thread, Google’s John Mueller explained that your pages do not have to be identical if you want to redirect page A to page B:
“If these pages are equivalent, even if they’re not 100% identical, I’d use a rel=canonical here. With that, all of the signals (such as links to those pages) that we have for the ‘set’ of URLs will be combined in your preferred version.
Using a noindex on the other hand would result in only one page being indexed, with all the other pages from that set - and any associated signals we might have - dropping out.”
