NSUserDefaults as the name suggests (vaguely) should be used for storing preferences and app settings only. You should not be storing critical data and or user data into them
- Easy to store and retrieve data.
- Useful for storing default values with minimum fuzz.
- Not suitable for large data sets
- Performance hit when you try to store and load large amount of data All or nothing approach
CoreData is a full fledged persistent framework which supports large data transaction
- Reliable framework to interact and query against data
- Can be extremely fast when setup correctly (with relationships)
- Powerful capabilities