Why Android>>>>iOS ?

There was a time when smartphones were in their infancy and every operating system had some killer feature that the other did not have. Recently, my sister who was using a cheap android phone for 2 years, decided to buy something premium. She asked me so my first question to her was-

What do you want - Android or iOS ?

She asked for advantages and disadvantages of choosing either and specifically for some killer feature.

Although she is now a proud owner of an iPhone 5S and is quite happy with it, I am still pondering over her question.

What do you guys think ?

P.S.- There is a similar post on Apple Core too.