One of Apple’s slogans is ‘It Just Works.’ If this is your first (smart) mobile phone or if you find it hard working with computers in general then Apple is more likely to be your sort of device.
At least in America, Windows Phone hasn't really taken off - as a matter of fact, even in a growing market Windows Phone market-share is shrinking. It grew from 3.1% to 3.4% between 2012-2013, then fell in 2014 to 2.5% and in 2015 rose slightly to 2.6%. It has shipped 8.8 million unites in Q2 2015. This is paltry compared to the iPhone selling nearly 50 million units in the same quarter as well as Android (numbers unlisted)
Since the adoption rate of Windows Phone is pretty low due to Microsoft being a bit late to the mobile game with this OS there are few apps and games available when compared to iOS and Android.
Developing for Windows Phone 10 will make it very easy to add your app store to the Windows 10 Store as well (available on all 110 million Windows 10 users' machines)