Position of Content Types

Hi

Whats the difference in creating a Content Type in the Root Site collection to that of a subweb?

I've noticed when created at Root lovel its available to all sub-webs wheras if I create at web level its only available to sites below.

Is there any difference when it comes to associating workflows to Content Types or anything else?

I think when a root CT is used in a subweb, SP makes a local copy at subweb level, so it behaves as if the CT is locally created. Is this true?

Thanks