Pros of XWiki:
- open source and open community
- development platform. Confluence is a wiki. XWiki is a development platform on top of xwiki you can build collaborative applications. For example: XWiki Enterprise (enterprise wiki), XWiki Watch (Collaborative RSS Reader), Chronopolys (Project Management), XWiki Workspaces (Group collaboration), etc.
- stronger customization. Everything is customizable in XWiki and almost everything is an application. For example the Blog feature is just an application. You want several blogs instead of one? Just modify the application to use several. You want to add a new blog feature? Just add it easily by simply editing pages in the wiki, etc.
- easier integration with external content thanks to XWiki's scripting features (Velocity and Groovy scripts).
- multiwiki feature, i.e. the ability to run tens of thousands of wikis on a single JVM and thus on a single machine. The multiwiki feature (XWiki Enterprise Manager) also allows centralized administration of all the wikis, ability to create template wikis, and more.