Archived Apps in XCode are a great way to submit new versions to iTunes Connect because they are automatically grouped, tagged and re-signed in the process – you don’t need to manually find the compiled App, zip it & upload with the Application Loader.
If you start at a new Mac without data migration, you can simply copy the folder with all archived App versions to your new users library.
You can find it here:
/Users/<USERNAME>/Library/Application Support/Developer/Shared/Archived Applications
Or, if you develop at different Macs, symlink that folder to your Dropbox to have them accessible everywhere :-)