SharePoint and Confluence are two separate platforms for different purposes which do share similar functionality, are based on completely different technology, and for which can be difficult to move users either way.
Nothing has really changed. SharePoint 2013 does bring more to the wiki world and is making strides towards offering what Confluence has but it has not caught up in my opinion as administrator of both. The best option, still, is to use both and let the users choose which platform is best for them. Get the SharePoint Connector for Confluence and make everyone happy.
The main difference is that Confluence is an enterprise wiki compared to SharePoint which is a Microsoft application platform which includes document management, a wiki, web application hosting, social media functionality and more. SharePoint is working its way towards offering the same functionality as Confluence, in a Microsoft way.
SharePoint still can't compete with Confluence as an Enterprise Wiki. It is possible to get results from SharePoint if you are willing to throw enough resources at it. SharePoint will do as a basic wiki for an organisation that doesn't have Confluence or another wiki specific solution.
Confluence is still superior for information input and management of wiki pages. YMMV. The Confluence page hierarchy, plugins, security, user macros, page alias, metadata macros, scaffolding and user interface offer a superior wiki platform over SharePoint.
SharePoint is a superior DMS. Confluence is a better wiki. Both have online Office document editing capabilities, although SharePoint may be better. Both have search. SharePoint's Site Collection / Sites / Subsites structure may be more suitable than Confluence's site structure for organisations who need a deep site hierarchy.
Moving dedicated Confluence users to SharePoint is difficult, especially for users of Confluence plugins. Migrating data from Confluence to SharePoint can also be difficult even with migration tools.
SharePoint still takes a lot more resources - servers and administrators - than Confluence. SharePoint requires more planning, configuration, technical expertise, and time to implement. SharePoint requires much more system knowledge to administrate. Both could do with improvements for data export and data import.
When considering performance, SharePoint is still slow compared to Confluence. Waiting for pages to load is just painful.
User training and education about SharePoint is a serious issue. As a general rule you can grant a user access to Confluence and let them just go for it. For SharePoint basic training is needed to avoid problems later on.
Some users will try SharePoint and like it. Most won't. The only way I've seen to get people to move is to turn Confluence off. Most sites will run both. Considering that Confluence is quite cheap to licence and maintain the benefits outweigh the costs.
Your question has been asked here repeatedly for years now especially from people who think that SharePoint and Confluence are the same because you can create and edit web pages in both. Higher up in the chain managers ask why we are paying for two products which do the same thing: no one understands why users will not voluntarily move to SharePoint from that perspective.
The only answer I have so far, barring turning off Confluence, is:
- Create a SharePoint site for each Confluence Space using the same space name as the site name
- Create the security groups in SharePoint as the same names as in Confluence
- Give users an introduction to SharePoint showing the basic functions including wiki pages, document management, web parts, apps, etc
- In Confluence edit the home page or sidebar to create links to the SharePoint site. In SharePoint create links in the sidebar or menu to the existing Confluence spaces
- Reduce the barriers to entry for users to use SharePoint as much as possible
- Wait and see who gives SharePoint a try
Good luck convincing people to use SharePoint over Confluence. Carrot, stick, or both? In your position I would find teams in the organisation who are not using Confluence to start using SharePoint. I would then find Confluence loving teams willing to give SharePoint a go, offering them extended support to bridge into the SharePoint world. With users started, I would build the community, documentation and support for SharePoint over time to give the Confluence stalwarts good examples of what SharePoint can do for them.