That results in a 301 redirect if you check the box "Additional URLs redirect to the default URL". If you don't, you'll get multiple URLs showing the same content, which is bad from a SEO perspective.
If you have lots of changed URLs it's more practical to use the IIS URL Rewrite module. I don't think Sitefinity can rewrite URLs, so you would need this module for that purpose as well. I never tried that though.