Android is defined by its diversity. It may be the most popular mobile operating system in the world, but it's also highly fragmented. If you're used to Android on one phone and buy a device from another manufacturer, you'll get a very different user experience.
Every company that manufactures Android phones pre-installs its own user interface atop the Android OS. This lets it customize the look and feel of home screens and offer device-exclusive features, but can make choosing between phones that much more difficult for you. While our Android phone comparison offers a great overview that considers build quality, performance, each phone's camera and much more, if you find yourself trying to decide between two different manufacturers, you should consider the OS experience each will give you.
Among Android phones, Samsung devices are by far the most popular, which makes TouchWiz the most popular Android UI. TouchWiz tends to have a bright, airy feel. It comes preset with a large weather and time widget on the home screen, and favors icons with drop shadows. Where a lot of modern design philosophy is moving toward flatter, more simplified imagery, Samsung icons are bold, rounded, and use lots of color.
TouchWiz is best known for its massive feature set, packing Samsung's devices with plenty of fun extras. Some of these features are useful; others can feel thrown together. Smart Scroll, for example, lets you scroll through documents and web pages by tilting your phone up and down, though its controls can take some getting used to. Smart Pause will track your eyes and pause a video you're watching if you glance away from the screen. Each feature is only available if the phone you buy has the hardware to go with it, of course, so check out the feature set before buying.
Of all the third-party Android overlays, TouchWiz is by far the most polished under the hood. You might not use all its features after all, waving your hand over the screen to change music tracks can feel a little silly but there's more than enough here to enjoy.
Where TouchWiz is bright and airy, HTC's Sense UI has a darker color scheme, with white text on a black background. Big screens consume more power when they display white pixels, so Sense's heavy use of black helps conserve battery life. Some users may find it a bit dark for their tastes, but we tended to enjoy the crisp, monochromatic iconography of Sense's widgets.
HTC Sense's biggest feature is BlinkFeed, an automatically updated, pictorial newsfeed for your home screen. BlinkFeed gathers stories from Twitter, Facebook, your calendar and various news sources around the web, and compiles them into a scrollable, tile-based view of what's happening in your world. It tends to split users many love it, but many ignore it completely. Thankfully, the most recent update to the UI lets you disable it if you want to, so you can enjoy the rich darks of the Sense palette without distraction.
LG Optimus UI
Named for the series of phones it has long powered, LG's Optimus UI sports some unique features that have won over more than a few fans. Chief among them is the surprisingly simple but entertainingly intuitive KnockON, which lets you turn your phone's display on and off with a simple double-tap of the screen. It takes a bit of getting used to we're used to thinking of a black screen as something we can't interact with but once you stop reaching for a power button, you'll wonder why every phone doesn't let you do the exact same thing.
There are other plusses to LG's UI, too. Where other Android installations require you to download additional software if you want to customize your launcher, LG lets you tweak things to your heart's content from the moment you get your phone. You can pick which icons your applications use without having to rely on something from a third party. And LG's interface is among the most graphically beautiful we've seen, with stunning unlock animations and sweeping transitions.
Android 4.4: KitKat
Every version of stock Android is named after an alphabetically sequential dessert. The third version, for example, was named Cupcake; the fourth, Donut. While Samsung, HTC and LG struggle to update their phones to Android 4.3, Google has already launched Android 4.4: KitKat.
Found on Motorola's Moto X and Google's own Nexus 5, KitKat features bigger, brighter icons with slightly smaller text than previous versions of Android. It offers improved graphics and support for things like translucent interface elements, which help it compete with Apple's aesthetically impressive iOS. It's also been streamlined to run well on weaker hardware, so if you wait a few months, you're likely to start finding its improvements on budget phones.
One of its biggest core features of KitKat is its extensive integration with Google Now. Google Now has always let a phone bring up information that you need, when you need it, without your having to ask for it. It will display your airplane ticket when you're at the terminal, or a loyalty card when you're in line at your local Starbucks. With KitKat, however, you also get easy, voice-activated control over your phone from any home screen. Want to ask a question? No need to press any buttons; just say, "OK, Google," and ask.
There is much, much more to each Android UI than we could fit in this brief overview. Each caters to a different audience, and each offers great features for that audience. Do you consider yourself an Android purist? Then stock KitKat is the way to go. Want easy, user-friendly customizability right out of the box? LG has you covered. Love the idea of BlinkFeed and a dark, modern look and feel? HTC's Sense pairs beautifully with the aesthetic excellence of its line of phones. Or perhaps you love whiz-bang features and tried-and-true polish if so, there's no beating Samsung's TouchWiz.
Whichever you choose, remember that all versions of Android can be easily tweaked with new launchers and fun applications from the Google Play store. If you're feeling adventurous, you can even root your phone and get complete, system-level access to its underlying mechanics. Numerous though the variants of Android are, they all provide more customizability than you'll find on any other smartphone.