When comparing Precursor vs Diagrams.net, the Slant community recommends Diagrams.net for most people. In the question“What are the best mockup and wireframing tools for websites?” Diagrams.net is ranked 6th while Precursor is ranked 9th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free tier
A free tier with all mockup functionality is available. Free tier is limited by lacking ability to save mockups privately and additional services provided by Precursor like voice chat and registered subdomains.
Pro Collaborate in real time
Share a link with teammates and they can jump right into your doc. You'll see their changes as they happen, and the built-in voice chat makes design meetings effortless.
Pro Highly polished UX
Pro Rich functionality for a web-based application
Pro Integrates with multiple cloud storage services
Draw.io offers saving files directly to services such as Google Drive, OneDrive or Dropbox along with saving to to computer.
Pro Real-time collaboration
Pro Great flexibility customizing text labels
Pro Completely free
Pro There is also a Desktop version
Pro Good list of different output formats
Draw.io supports export for PNG, GIF, JPEG, PDF, SVG, HTML, and XML.
Pro Internet Explorer 6-8 and touch device support
Draw.io works with every browser (even IE 6) without plugins.
Cons
Con Really simplistic
Basic tools (line, square, circle) wich do no stick together: if you move a circle the attached line won't move making reengineering the model simply impossible
Con Import from Visio .vsd is useless
Even simple diagrams get all scattered.
Con Behaves strangely for certain diagram types
For example the snapping function for arrows doesn't work properly for the sequence diagram template.