A key difference is that POST Folder has a specific rate limit, while POST Command has a general rate limit for all possible commands. Additionally, POST Folder requires one call for each folder, which may require adjustments to your code's logic. Please refer to the documentation for additional details.
The legacy POST Command will continue to work for existing applications until early January 2022. We recommend that you start migrating your code now to POST Folder. If you have any questions or concerns about the endpoints, usage, or rate limit, please contact us via firstname.lastname@example.org.