The article conclusion is the key:

As computing becomes ever more mobile and more device-centric, stability and efficiency is key. One of the key reasons for the speed, stability, and power efficiency of the iPhone and iPad is that iOS is specifically tailored to the hardware. Windows 8 might be the fastest and most stable OS that Microsoft has ever developed, but it would be even better if it only worked on the Surface.

Simple as that. The dual OS strategy of Apple keep paying off…