The chief differences between Cloud Poodll and Classic Poodll are outlined below:
Cloud Poodll plugins are independent
The Classic Poodll plugins all rely on the Poodll filter and so to use them you subscribe to the Classic Poodll package, and you install the Poodll filter and any of the Classic Poodll plugins that you need. Cloud Poodll plugins have no dependencies and you can install and subscribe to them individually.
Cloud Poodll plugins are HTML5 only
Classic Poodll can fall back to Flash and other ways of recording if the browser does not support HTML5. Cloud Poodll only does HTML5 recording.
See the chart on the browser HTML5 support page for more details.
Cloud Poodll stores files in the cloud
Classic Poodll saves audio and video recordings in your Moodle site's data directory. Cloud Poodll stores recordings in the Poodll cloud. There are benefits to both ways. When recordings are saved in the Poodll cloud your site backup files stay small and you can schedule the files to "expire" after a fixed period (or not). The process is simpler too, so there are fewer points at which something might go wrong. When recordings are saved in your own site, it is easier to answer questions related to privacy of user data.
Cloud Poodll can generate transcripts
Cloud Poodll can generate subtitles and transcripts of audio and video recordings automatically.
Cloud Poodll has fewer plugins
Classic Poodll has plugins for quiz questions, database activity fields, repository, assignment submission/feedback and the Atto and TinyMCE editors. Cloud Poodll currently just has plugins for the Assignment Submission and Atto editor. Assignment feedback, TinyMCE and the quiz question plugins are coming soon.