You can't actually tell which android version is stable because OEM use their own skin above the pure android software. The stability depends hugely on the skin. For example the browser on the vanilla android 4.0.4 is very fast and stable but the browser on HTC One X is very choppy and slow even though it is running android 4.0 . It depends on the skin. Gingerbread running on xperia devices is far more stable then what is used in LG devices. If you are asking for vanilla experience then android 4.1 is the most stable.
