Blogging SEO Question

On this blog, there are two widgets that get users to see old articles.

One is the archives-based widget which first takes them to  a URL that involves the term "archive".  For instance:
http://learn-to-market-online116.blogspot.com/2011_10_01_archive.html. Then, by clicking on the article title, you get to the article with a URL that starts with the date:
http://learn-to-market-online116.blogspot.com/2008/12/marketing-plans-for-2009.html .  This is I believe that cannonical url for the content on that page.

Another way of getting to that content is through the tags or categories widget.  So if I click on social bookmarking (4), i get a page titled 'http://learn-to-market-online116.blogspot.com/search/label/social%20bookmarking" which has links through titles to http://learn-to-market-online116.blogspot.com/2010/07/how-many-and-which-social-media-icons.html.

Here's my question: Is one widget any better for SEO than the other? Does having both help or hurt.
Secondly, the URLs all have the date added to them. Is that good or bad? Do I have control over it?