My preference would always be to enforce a single URL via redirects wherever possible as this may provide a slightly better experience for users than the canonical tag and it also helps to ensure that all inbound links point to the same URL.
I think the canonical tag is more useful in a situation where multiple URLs are required to effect a slight variation in content (such as ?sort=asc vs. ?sort=desc) but only one version of the page needs to be indexed by search engines.
Of course, the canonical tag could be considered for any of the above scenarios if a redirect is not possible (mod_rewrite not enabled, non-Apache server etc.)
Good question, David.
My preference would always be to enforce a single URL via redirects wherever possible as this may provide a slightly better experience for users than the canonical tag and it also helps to ensure that all inbound links point to the same URL.
I think the canonical tag is more useful in a situation where multiple URLs are required to effect a slight variation in content (such as ?sort=asc vs. ?sort=desc) but only one version of the page needs to be indexed by search engines.
Of course, the canonical tag could be considered for any of the above scenarios if a redirect is not possible (mod_rewrite not enabled, non-Apache server etc.)