My company (XWiki SAS) had a booth at the Paris Open Source Summit 2017 (POSS) and we also organized a track about "One job, one solution!", promoting open source solutions.
I was asked to talk about using XWiki as an alternative to Confluence or Sharepoint.
Here are the slides of the talk:
There were about 30 persons in the room. I focused on showing what I believe are the major differences, especially with Confluence that I know better than SharePoint.
If you're interested by more details you can find a comparison between XWiki and Confluence on xwiki.org.