The usefulness of dynamic and static URLs are unique in their own ways. Here are some valuable and critical  information regarding the both of them.

The difference in between
The  static URL does not change. But, ‘no change’ does not mean that it is devoid of any URL parameters. The static URL may appear like: http://www.example.com/archive/january.htm. They can be found when you search on Google by entering the keywords  filetype:htm. Static URLs need more time for updation. As  every single page needs to be hard-coded in case of static URL,  with the increase in the amount of information, updating continues to takes further more time.

Dynamic URLs are used when the content of a website is stored in a database and pulled for display ‘on pages on demand’. Here, the site  does the service of a template for the content. An URL  of dynamic category looks like: http://code.google.com/p/google-checkout-php-sample-code/issues/detail?id=31.

Against an established myth that dynamic URLs escape crawlers, Google says that dynamic URLs can in fact be crawled. However, there may be some problems if the URLs look static or hide parameters that otherwise offer Googlebot valuable information. A dynamic URL can appear as static if reformatting is avoided.

In case of dynamic URLs, the number of parameters are not restricted. You are free to remove the unnecessary parameters from the Googlebot’s  point of view.