1) Business Unit Hierarchy | The ability to divide the data into isolated silos with bridges of controlled access aligned to the defined.(Security + Performance)
2) Out of the Box Entities | The configuration of entity permissions when the entity is doing backend functionality for the system and not something such as Account, Contact....
3) Management Hierarchy | The ability to give permissions to a manager based on the permissions and data and functions that their child team member has access to.
4) Field Level Security | The ability to mask, encrypt and control who can see a specific field within an entity
5) Entity Security | The ability to control who can Create, Update, Read, Delete, Append, Append to and Share specific out of the box entities or custom entities by Organization, Business Unit, Business Unit Hierarchy or User Ownership.
6) Flow Context | The ability to control what permissions a flow runs under, either Contextual User or a Defined User such as a system account.
AND there is more so when considering "Building Your Own", consider if you want to recreate the concept of Role Based Entitlement