I work with Deon every day (in my team and with customers), and I am really impressed by some of the features - also compared to Mural or Miro.
I like about Deon is the stability and that all basic functions/features are well implemented. The focus here is really on the central elements.
Also, the copy&paste function is better integrated. With Mural, I had some trouble when copying Post-its.
Better are also the export functions (pdf, png, ppt, ...) and the compatibility with SharePoint / Office. This helps a lot with documentation after workshops.
Also excellent is the zoom factor and the infinite board. Others are often limited to a certain size. With Deon you can create massive walls.