SQL databases are relational, structured, and use a predefined schema with tables consisting of rows and columns. They are best suited for applications requiring ACID (Atomicity, Consistency, Isolation, Durability) compliance, such as banking systems or enterprise applications. Examples include MySQL, PostgreSQL, and SQL Server. NoSQL databases, on the other hand, are non-relational, flexible, and can store data in various formats such as key-value pairs, documents, or graphs. They are ideal for applications that require scalability, high availability, and handling large volumes of unstructured or semi-structured data, such as social media platforms or real-time analytics. Examples include MongoDB, Cassandra, and Redis. I would choose SQL when data integrity and structured relationships are crucial, while NoSQL is preferable for handling dynamic and high-scale applications where speed and flexibility are more important than strict consistency.