Hi, The Dynamic URL's created while designing websites in Joomla are worth effective in rankings of Search Engines or they are really need to be rewritten for Good Search engine rankings.
Dynamic urls should be re-written to be more Search Engine Friendly. The out of the box SEF plugin works reasonably well, but for real good results look at SEF404.
To get good ranking on google or other search engines you need to re-write urls . Check for global configuration.
Dynamic URLs will not work with any Search Engines. Search Engines will give more importance to SEO Friendly URLs so I will prefer to use SEF URLs module in Joomla.
Activating the Joomla Friendly SEF Url module is one of the first thing I do when I create a new Joomla website (SEO Settings window, global configuration, right column). It will help Search engines' robots to crawl and index your pages more effectively, and the built-in option is really becoming better and better with every Joomla update. And yes, if you want to go a little further and customize your urls and metadata, don't hesitate to try Joomla SEF404.