How can I compare the parameters of storage policies, looking for an export rather than calling up the interface side by side.

The commcell configuration report is what you are after. You should be able to use the options to filter on storage policies:

https://documentation.commvault.com/2023e/expert/commcell_configuration_report_overview.html

The CommCell Configuration Report Provides a high-level view of the settings that are configured for the CommCell, including properties, alerts, users/user groups, agents, storage policies, etc.

You can use the CommCell Configuration Report to review a wide range of CommCell contents, settings, and properties.