Why are scans with SpaceObServer slower than TreeSize scans?
TreeSize Professional scans file system structures as needed and holds a snapshot of the scan in your system memory.
SpaceObServer archives all needed file system information in a backend database. This is needed to calculate size development information for the scanned directories and enables you to filter the file system tree without the need of a rescan.
Building up the SQL database is quite costly. This is why the initial scan of SpaceObServer runs very slow compared to the scans of TreeSize Professional.
Note: The update scans of SpaceObServer do only need to update the changes on your file system in the database. So generally the update scans run faster than the initial scans.