See this support document for help http://support.apple.com/kb/HT1495, however, there is no way that iTunes can treat two devices as the same, unless you have the settings in iTunes for the two devices set the same. Each iOS device is identified differently in iTunes. It is how you set iTunes to handle the two devices that can differ.
This site contains user submitted content, comments and opinions and is for informational purposes only.
Apple disclaims any and all liability for the acts, omissions and conduct of any third parties in connection with or related to your use of the site.