When comparing QtCreator/Qt vs DiffMerge, the Slant community recommends DiffMerge for most people. In the question“What are the best Linux diff tools?” DiffMerge is ranked 9th while QtCreator/Qt is ranked 14th. The most important reason people chose DiffMerge is:
DiffMerge is free of charge to download and use for both commercial and open source projects. There's no license needed. However, people who want to contribute to the project monetarily [can do so](https://www.sourcegear.com/diffmerge/register).
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Pros
Pro Visual GUI designer
QtCreator has QtDesigner component, allowing you to design a GUI in visual mode instead of raw code.
Pro Ready-made classes for most used tasks in desktop app development
Launching external applications, getting environment variables, putting tasks to separate threads, offscreen painting, transparent loading of most used image formats, even such helpers as opening files in default application configured in OS, cross-platform (!).
Pro Cross platform
Qt supports most popular platforms including Linux, FreeBSD, Windows, and Mac OS X. This allows developers to easily port applications to different platforms.
Pro Completely free
DiffMerge is free of charge to download and use for both commercial and open source projects. There's no license needed. However, people who want to contribute to the project monetarily can do so.
Pro Cross platform
DiffMerge is cross platform and is available for all major operating systems. This means WIndows, Linux and OSX
Pro Folder compare
Pro Three way merges
DiffMerge supports three way merges.
Cons
Con Vendor lock on QtCreator
It's not simple at all to use Qt in a different IDE, and you'll lose QtDesigner.
Con Big overhead
Con Startup time can be slow
DiffMerge's startup time can be quite slow sometimes.