If you want your data to have a one-to-one relationship with a CRM record, the best HubSpot data representation tool is:

In the HubSpot Data Integration certification, custom properties are the best tool for representing data that has a strictly one-to-one relationship with a CRM record. While "Objects" (standard or custom) are designed to represent distinct entities that can have complex one-to-many or many-to-many relationships through associations, a property is a specific field contained within a record. For instance, if you need to track a unique data point like a "Subscriber ID" or "Shirt Size" for an individual contact, creating a custom property on the Contact object ensures that each piece of data is directly tied to exactly one record. This approach maintains a clean database architecture by avoiding the unnecessary overhead of creating separate objects for data that does not need its own independent timeline, associations, or distinct record identity.