When comparing Kaleidoscope vs AraxisMerge, 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 AraxisMerge is ranked 15th. 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 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 Point and click merging
AraxisMerge has a feature which is very helpful especially for beginners. By clicking on different parts of a text file you can select all the parts to added in a final merged file. The comparison display also updates real-time as the merge happens.
Pro Directory comparisons
AraxisMerge supports comparing different directories with each other.
Pro Beautiful interface
Pro Three way merges
AraxisMerge supports three way merges.
Pro Update alternative files Word, PDF and even images
Pro Works great on large files
Cons

Con Mac OS only
Kaleidoscope is a Mac OS X only app.
Con Paid software
Kaleidoscope is not free, costing $69.99.
Con Commercial
AraxisMerge is not free:
$129 Standard and $269 Professional
But this is peanuts for a tool that you can use all day for the rest of your developer life.
