When comparing Diagrams.net vs UX-App, 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 8th while UX-App is ranked 25th.
Ranked in these QuestionsQuestion Ranking
Pro Completely free
Pro Rich functionality for a web-based application
Pro There is also a Desktop version
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 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.
Pro Real-time collaboration
Pro Mock up & prototype in the browser
Allows you to mock up with real HTML, and present expressive prototypes in the browser. Has lots of conveniences like team chat, notes, and a share link to present prototypes.
Pro Long free trial & cheap subscription
It's possible to start without creating an account. Creating a free account extends the trial, and the memberships are cheap @ $5/month.
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.