When comparing Kaleidoscope vs DiffMerge, the Slant community recommends DiffMerge for most people. In the question“What are the best folder/file compare/diff tools for either OSX, Linux or Windows?” DiffMerge is ranked 8th while Kaleidoscope is ranked 12th. 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).
Specs
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Pros

Pro Simple UI
Kaleidoscope has a beautiful and simple UI. It displays the two files that are being compared side to side, highlighting all the differences in a way that's easy to understand.
Pro Diff within a line
When working in code, line-by-line diff can still be hard to spot small changes within the line. Kaleidoscope will highlight what has changed.
Pro Supports comparing folders

Pro Image difference viewer
Kaleidoscope supports image diff viewer in addition to git diff. It's able to find even the slightest changes between two versions of the same image.
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 Mac OS only
Kaleidoscope is a Mac OS X only app.
Con Paid software
Kaleidoscope is not free, costing $69.99.
Con Startup time can be slow
DiffMerge's startup time can be quite slow sometimes.
