The aim of both the Daily DPS Scanner and Initial Website Scan is the same: to identify third party technologies triggered from your website and help integrate them into your Consent Management Platform (CMP).
The major difference is that the Initial Website Scan will only perform a basic scan of your website enabling a customer to get an idea of what third-party technologies are being triggered from their website thus helping to select the appropriate ones to store in the CMP. This is especially helpful for clients in the on-boarding process.
Whereas, the Daily DPS Scanner runs daily to give a more extensive set of data which not only contains third-party technologies but also piggybacked services. An example is the service "Doubleclick", which is reloaded by default from every YouTube video.