After reading a lot of blogs and articles with all sorts of opinions about Core Data and my personal experience with it being very limited since I have worked in projects that used it but they were already setup and configured for it, I have also found some other 'apparently impressive' technologies like Realm and YapDatabase (I am always hesitant to depend on external companies/technologies especially if they are closed source).

About the data that will be stored, basically user accounts, like contact information: basic info (name, emails, addresses, phone numbers, etc.) and extended info (birhd date, other important dates, notes, social usernames, etc) and relationships between users.

If you have any experience with several of them, what would you use in a fresh start?