When comparing Draw.io vs nomnoml, the Slant community recommends Draw.io for most people. In the question“What is the fastest way to create and edit UML diagrams?” Draw.io is ranked 3rd while nomnoml is ranked 7th.
Ranked in these QuestionsQuestion Ranking
Pro Rich functionality for a web-based application
Pro Completely free
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 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.
Pro Real-time collaboration
Pro Everything runs client side
You can use the website even for sensitive content as nothing is sent to the server.
You can override the global styling for the diagram and you can also define custom types for the entities. It is really powerful.
Pro Free and open source
You can extend it, if you find something missing!
Pro Automatically saves
The browser-based tool automatically saves your changes to your localStorage, which is a nice and handy feature.
Pro Text format
The tool generates diagrams from a simple text format, which is easy to edit and you can even version control it.
Pro Fully fledged
It knows many types of UML entities and relationships so you will barely miss anything.
Con Behaves strangely for certain diagram types
For example the snapping function for arrows doesn't work properly for the sequence diagram template
Con Import from Visio .vsd is useless
I opened a simple diagram and it's all scattered.
Con Can't connect entities on different levels
The tool can't connect entities on different levels, for example a class and a class inside an other package.