They are essentially the same thing with one minor difference. All contributions that make up a build result in Jazz have a primary extended contribution type id. This allow consumers of build results to figure out what type of contribution they are looking at and take appropriate action.

ArtifactFilePublisher automatically defaults for the client the appropriate id so that file published shows up in the downloads tab in the build result editor and any other place that understands that particular extended contribution id.

FilePublisher on the other hand requires the client to tell us what the extended contribution id is. It's designed for individuals that are contributing their own types of file based contributions to build results and need their own id. An example of this is the code coverage tools in Jazz. They use it so they can publish converage result to a build result and then show them accordingly in a tab they contribute to the build result editor.

Don Weinand
Jazz Team Build