Drupal and SEO: A comparison
I've recently been noticing a trend in how other websites are handling Clean URLs and it isn't good! Most websites don't appear to have the same luxury we have with Drupal (a concrete URL Alias system provided by the Path module). Although the URL Aliases can sometimes be a bit of a burden on larger sites, as the table can easily enter the tens or evey hundreds of thousands of entries, it provides (if used correctly) a very effective 1:1 relationship.

