Hi there everyone!

I was hoping to find out if anyone has anything to share when comparing the
current state-of-the-art operating systems out there for mobile phones based
on these criteria:

(1) How many people out there in the market uses phones based off this OS
(2) Energy Efficiency
(3) Ease and time needed for developing apps
(4) Cost

If you could point me to some web resources(URLs) out there , that be great!

Thanks