Migrating a SQL data pipeline from Stitch Data to dlt involves recognizing the need for more control and customization over data migration, considering the financial costs associated with using Stitch Data, and taking advantage of the scalability and speed offered by open-source tools like dlt. The process involves disabling the existing Stitch Data pipeline, creating a new dlt pipeline with incremental loading, running the pipeline, and merging historical data from both sources into a unified view. By following these steps, organizations can reduce their data ingestion costs and improve ingestion speed while maintaining data integrity.