Cellular 

The choice of the smartphone between two operating systems dominating the market (android and ios)

android

Lots of freedom in the presentation of interfaces, number of home screens and size of widgets to display, highly customizable. Integrates well with the Google service (photo, maps, etc.) but updates are not always accessible.

ios

Easy to use, simple and elegant design, it integrates easily with other devices at home of the same brand and will interact (ipad, laptop, smart watch...) Less customizable, the operating system is the same on each iPhone.

Factor to consider

More efficient processor and new generation network type on most new phones. This factor to choose according to the utility of the user, this influences the price.

A larger screen makes it easier to use the keyboard, a smaller one will fit better with one hand.

Larger processor and screen reduces battery life especially if it is very thin.

Storage capacity for applications, photos and videos.

Processor performance for photo and video.

The NFC chip allows contactless data transfer such as credit cards. Useful for mobile payments.