That's up to you, but I'm not suggesting that you actually sync it... just look if one or both is added and active.
This is because when I recently got a new phone I added that to iSync and at the same time turned off syncing for my old phone (it still appears in iSync but inactive) and the tool tips on the Bluetooth button in my Address Book now refers to my new phone (and I cannot remember doing anything in Address Book to make it so).