Fabric OneLake shortcuts vs ADLS Gen2 mounts: what actually works in production

If you've just moved a team onto Microsoft Fabric, the "how do I read our existing ADLS Gen2 data?" question comes up in the first week. Two patterns are on the table: OneLake shortcuts - Fabric's newer, metadata-only references that make external data appear as a Lakehouse table ADLS Gen2 mounts - the mssparkutils / notebookutils pattern that's been around since Synapse The docs describe them as roughly interchangeable options. They aren't. We've now shipped both across ~15 Fabric projects and