As the Main Difference Lies in the Scope of the Data Source.
SharePoint Rest API designed to work specifically with SharePoint sites and content.
While Microsoft Graph API is a more general API that can be used to access data from various Microsoft 365 services.

SharePoint REST API:

• An architectural style for web services.
• Allows communicating between two software programs through HTTP.
• You can use different methods/verbs like GET, POST, PUT and DELETE
• It is essentially based on the user context.

Graph Api in SharePoint:

• Allows accessing the SharePoint data but not only data. you can access the wide resources provided by MS365 Tenant.
• It is based on the entire environment.
• It becomes useful when you wish to link several resources types in one point.