What is one of the main advantages of the Core Components in AEM?

The primary advantage of the Core Components in Adobe Experience Manager (AEM) is their ability to promote reusability and adherence to best practices. Core Components are pre-built, standardized components that streamline the development process by providing a library of frequently used functionalities.

This means that developers can leverage these components instead of starting from scratch, which not only accelerates the development cycle but also ensures that the components are built following AEM's best practices. This reusability reduces redundancy and allows for consistent user experiences across different pages and projects. Additionally, since these components are designed to be easily customizable, they can be adapted as needed without needing extensive custom development, thereby enhancing efficiency.

In contrast, the other options present points that are not aligned with the benefits of Core Components. For example, custom development is not always necessary due to the availability of these pre-built solutions, and concerns about upgrades or being outdated are addressed with regular updates and improvements from Adobe.