The Samsung Galaxy S4 shipped with the slightly newer 4.2 version of Google's Android operating system, as opposed to the HTC One's 4.1.2. But a future Android update will level the playing field at some point.
Even though both smartphones run Android, they have distinctly different user interfaces. For example, the HTC One comes with a new version of HTC's GUI overlay called Sense, which has a simple design and also integrates live news and social media updates through the new "BlinkFeed" feature; users can switch back to the older, busier version of Sense.
The Samsung Galaxy S4, meanwhile, uses the same TouchWiz interface as the Galaxy S3 and comes with other compelling features: Air Gestures, which allows users to control apps and features without actually touching the screen; Smart Scroll, which automatically scrolls the display when the device is tilted at an angle; and Smart Pause, which detects when users aren't viewing the display and pauses video. The HTC One has a simpler, cleaner interface but the Galaxy S4 has more cutting-edge technology.