There are good reports and comparison sites, both paid and free, that can help you understand the pros and cons of the different vendors for each type of intranet software. Some good intranet software reviews include:
Intranet CMS: A Guide to Choosing Intranet Software
SharePoint Intranets in-a-box Report V5.5
G2
Independent Intranet Report
9 Best Open Source Intranet Software for 2021
The Best 7 Free and Open Source Intranet Software