I have no experience with draw.io. What is this? Why should that be better than the Microsoft Visio we already have?
Instead of downloading a diagram-image from your Confluence, tweaking it, exporting it and uploading it back, with draw.io you work where your diagram is: Your Confluence. So editing a diagram together with your colleagues is possible (even in realtime), sharing is easy, there is a huge range of export-possibilities (including visio format) and on top its way cheaper whilst available for any Confluence user.
So, deciding which tool is better in general isn’t always clear (well, draw.io online is free), but when it comes to integrating a diagraming tool into Atlassian products, draw.io is the tool to chose.
Draw.io is a completely free online diagram editor that allows an open platform to create and share diagrams applications in real-time collaboration. It is easy to use and offers saving files directly to services such as Google Drive, OneDrive or Dropbox along with being able to save data to a desktop computer. Also, plugins for Atlassian Confluence and Jira are I’m included in these features, so it is best to keep that in mind when deciding which platform to choose from. It’s other notable features include toolbars that offer hundreds of visual elements, which can be positioned with drag & drop, and can be adjusted, moved, scaled and rotated at your leisure. Draw.io is known for its rich functionality that is exceptional for a free web-based application.
Microsoft Visio on the other hand costs a lot more money and does not integrate well with office suite or Atlassian software. It is also more suited for small to medium sized businesses as opposed to Draw.io which is suited for freelancers, small business, medium size businesses, and large enterprises. However, it is easy to use and is the industry standard diagram creation software.