There are roughly three major differences between the Free and the Premium Plans. In addition to all the functionality on the Free Plan, you get access to the following features on Premium:
Analytics: Access to in-product Analytics for trend analysis on Inspections, Actions, and Issues.
Integrations: Connect external business systems (Sharepoint, Dropbox, etc.) with integrations.
Unlimited Full Seats: On the Free Plan, you are limited to 10 team members, whereas on the Premium Plan, you can continue to expand your team well past 10.
Free Seats on Premium: Use Free Seats on your paid Premium Plan for limited platform interactions. Free seats can access and interact with all Heads Up, Actions, and Issues activities on your account without needing to pay a full license fee. Free Seats are great for bringing in your contractors, suppliers, or casual staff who may only need to use more collaborative areas of the platform.