✅ The Pros of DotNetNuke are:
It is the largest and most successful open source project in the Microsoft ecosystem
It has the largest commercial 3rd party market for a .Net CMS
The #1 most widely-deployed .Net based CMS
Widely adopted and supported by Microsoft
It's free! (but also has fully supported commercial versions for more serious organizations)
❌ The Cons of DotNetNuke are:
It's not based on MVC like Orchard. Note that this may not be a con for your organization
It is missing some enterprise features like those in Sitecore, EpiServer and SharePoint