Data classification:
The key factors to consider in deciding on the optimal storage solution are: how to classify your data, how your data will be used, and how you can get the best performance for your application.

What are the main operations on the data, ACID-compliant?
OLTP (Online Transaction Processing)
OLAP (Online Analytical Processing)

Correct storage solution can lead to better performance, cost savings, and improved manageability, after data classification.

Data classification: Semi-structured
Azure Cosmos DB
Azure SQL Database

Data classification: Unstructured
Azure Blob storage

Data classification: Structured
Azure SQL Database

Storage service

Storage service:

Storage account contains all Azure storage data objects: blobs, file shares, queues, tables, and disks.

Data store decision tree – Azure Application Architecture Guide | Microsoft Docs