Which is the most efficient way to move large amounts of data between instances?

"Export to Data Package" is not a standard ServiceNow feature for raw data transfer between instances in this context.

Exporting data to XML provides a structured format that can capture a large volume of records and their field values from a table. This XML file can then be easily imported into another ServiceNow instance, making it highly efficient for transferring extensive datasets while maintaining data integrity.

Update Sets are designed for transferring configurations (metadata and application changes), not for moving large volumes of transactional or record data.

"Export to Zip" is a generic file compression method and not a native ServiceNow data export method for structured data transfer between instances.