Changing existing category structure

Is it worth it?

If you have an existing directory, with something like this
http://www.directory.net/index.php?c=35

But this category is a PR4. Changing the url rewrite to something like
http://www.directory.net/category/subcategory
Makes it better for SEO, no doubt but the PR is gone. Is it worth it to make the change?

 

What exactly is the difference

 

there is no difference in those urls

 

Sorry about that, I meant changing it to
http://www.directory.net/category/subcategory

 

http://www.directory.net/index.php?c=35
Can't get pagerank, Google doesn't assign pagerank to dynamic URLs
(at least that I know of)

 

When changing structure, just 301 redirect the old URL to the new URL and Google will reassign any page rank.