best is what works best for you and has everything to suite your needs, best for me might be really bad and worse for you, but out of them three i only had ios so i cant really vote and give an honest answer
The latest ios is suppose to be the best one theoricaly, but this is not proved in practice. For me i will say that the best ios at the moment is 4.3.3 and this is only according to me, others might think else.