When comparing Dia vs LibreOffice Draw, the Slant community recommends Dia for most people. In the question“What are the best flowchart / diagram softwares?” Dia is ranked 13th while LibreOffice Draw is ranked 14th. The most important reason people chose Dia is:
Has flowcharts, uml, chemical engineering, electronics, and dozens of other complete sets, built in.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Tons of icon sets
Has flowcharts, uml, chemical engineering, electronics, and dozens of other complete sets, built in.
Pro Free and open source
Pro Custom gzipped XML format
Pro SWF Flash file export
Pro Free and open source
LibreOffice is available for free with code available here. It's licensed under LGPL v3 with new contributions dual-licensed under MPL.
Cons
Con Unmaintained
Dia has not been updated since 2009. It's already a very complete piece of software, but still sad.
Con UX is a joke
UX is not good enough. For example, to edit element text you must double-click it, then click text box, and then you can start typing text.