When comparing Kompare vs Kaleidoscope, the Slant community recommends Kaleidoscope for most people. In the question“What are the best folder/file compare/diff tools for either OSX, Linux or Windows?” Kaleidoscope is ranked 12th while Kompare is ranked 19th. The most important reason people chose Kaleidoscope is:
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.
Specs
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Pros
Pro Can create patch files
Kompare can create a patch file which lists the differences between two files. Patch files created this way are also compatible with the patch files created by the CLI diff utility.
Pro Supports comparing directories
Kompare can compare both files and directories.
Pro Configurable hotkeys
Because it's a KDE app, all the hotkeys are configurable

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.
Cons

Con Mac OS only
Kaleidoscope is a Mac OS X only app.
Con Paid software
Kaleidoscope is not free, costing $69.99.
