Core Data and UserDefaults are both important in making iOS apps, but they each come with some problems.

UserDefaults:

• Simple Data Only: It can only hold basic types of data, like words and numbers.
• Not for Big Data: It doesn't work well with large amounts of data, which can slow things down.

Core Data:

• Hard to Learn: It can be tricky to set up because it has a lot of features.
• Can Be Slow: If not used correctly, it might not work as fast as you want.

Solutions:

• For UserDefaults, use it just for small and simple data. If you have more complex needs, try using other storage options.
• For Core Data, take the time to learn the best ways to use it. This can help you make things run smoother and faster.