WordPress URLs and Creating Permalinks

If you had your choice would you want a link to a page on your site to have the following format:

http://www.longest.com/?p=1, OR
http://www.longest.com/2007/09/11/google-affiliate-program/

The latter if you would like to increase your pages relevancy in search engines such as Google.
Instead of just a variable as a number your link will be more relevant using the keywords from [...]