I am often asked what is the difference between Jellybean 4.1, 4.2 and 4.3
Attached is a comparison doc I found that should help.
Some of these are documented on Android developer site, plus some low-level additional informations that maybe relevant for app developers:
What's new in KitKat
What's new in JellyBean (v4.1, v4.2, v4.3)
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