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I chose Local Database, but that is my second favorite. My favorite isn't on your list and that is the background task so I can have my app wake up for alerts and other things. To be honest, I never considered even developing for Phone 7 without it because you couldn't even make a simple ToDo list with reminders program without a cloud service to send you reminders. And you'd have to be in a service area to recieve the reminder. Quite lame.