With Azure Blueprints, the relationship between the blueprint definition (what should be deployed) and the blueprint assignment (what was deployed) is preserved. This connection supports improved tracking and auditing of deployments. Azure Blueprints can also upgrade several subscriptions at once that are governed by the same blueprint.
Reference:
https://docs.microsoft.com/en-us/answers/questions/26851/how-is-azure-blue-prints-different-from-resource-m.html