Well, with the default WordPress Schedule feature, you can just schedule your WordPress Posts but you can not set any rules. Whereas using Auto Scheduler & Manual Scheduler features of WP Scheduled Posts PRO, you are able to set a certain set of parameters (such as day & time interval) in which you want your posts to be scheduled. This can come very handy to make your entire content planning process well-organized especially if you are running a multi-author website.
With the introduction of Social Share integration, you can now schedule your content and share them automatically on your social media platforms all within one tool. As a result, you don’t have to rely on any additional plugins to share your scheduled posts on Facebook or Twitter. WP Scheduled Posts PRO lets you automatically share your scheduled content on popular social media platforms such as Facebook & Twitter. WP Scheduled Posts offers visually stunning Schedule Calendar to see all your posts from one place with amazing drag & drop capabilities. You can also check the list of posts you have scheduled in a sitewide admin bar.
On the other hand, the Missed Schedule handler makes sure that none of your posts ever go unpublished at its scheduled time. Moreover, you can share your scheduled content automatically on popular social media platforms, Twitter & Facebook.
For further information, you can check out this documentation.