Mishaelo - 1:00 pm on Mar 13, 2013 (gmt 0)
I'm using alternate but with the hreflang tag which tells google these are similar pages with a different language.
That part is for G to display the correct language page depending the G domain search was made.
The canonical part is simply to override the parameters issues so when displaying a page on G in spanish it won't show the page with parameters and won't cause the pages to be considered duplicates (pages on the same languages)
I guess we just see this in a different way.
So who has the Matt Cutts hookup to settle this? :)