In most cases, Software-based Video Conferencing.
Using a software-based solution will provide you with the greatest flexibility for room choice, easier connection for participants (internal or external), and provide a good set of features, such as screen sharing.
Polycom video conferencing solutions are more advanced, this allows them to provide functionality above Software-based solutions. Including multiple camera and video streams, camera control of remote participants, greater audio control, and advanced integration with AV systems.