While it is technically possible to use a smartphone running an operating system other than Apple’s iOS or Google’s Android (Tizen, LineageOS, /e/ anyone?), the likelihood that you’re doing so is infinitesimally small. The majority of us are locked in a duopoly when it comes to mobile operating system choice. That’s not necessarily a bad thing: This two-way competition has pushed Apple and Google to create polished, feature-packed, and technologically potent phone software.
However, your choice of smartphone OS probably doesn’t concern the software’s technical capabilities or user features. It’s likely that you simply use what your social and family circles are using. If everyone you know uses Apple’s FaceTime for video calling, you don’t want to be left out of the party, and you wouldn’t want your messages to have green bubbles instead of the standard blue ones. There are cross-platform options for most functions, but built-in functionality and consistency usually trump third-party options. We judge the smartphone OSes in various aspects.