Take a look at Macworld's: iPhone vs Android: Why the Apple iPhone beats Google Android.
Smartphone makers take it in turns to trump each other for storage, processor speed and camera megapixels, but it’s the largely software - the mobile OS - that makes the biggest difference to your everyday use.
We're not talking about just the interface. It's the features the software offers, plus the depth and breadth of apps available for the mobile OS which make a difference.
It's all very well being able to download the big hitters such as Twitter, Facebook, Angry Birds and BBC iPlayer, but what about the smaller apps such as online banking, other catch-up TV services and more? If your chosen mobile OS doesn't have these in the app store, your smartphone will be more limited than you might want.
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Popularity is not necessarily the best guide either. The Apple iPhone quickly stole market share from BlackBerry and Nokia, but now plays second fiddle to Google Android in terms of the number of devices sold.
A resurgent BlackBerry - thanks to the recent launch of the BlackBerry 10 OS along with a more consumer-friendly BlackBerry Z10 handset - could win back former fans.
Microsoft’s Windows Phone 8 isn’t out of the running either. It's certainly one of the 'big four' mobile OSes and has its own strengths and weaknesses.
It may be that you already have an iPhone or Android smartphone and would prefer to stick to what you know, but with every high-profile handset launch and mobile OS update, the competition gets stiffer. The Android or iOS device of three years ago is barely recognisable from today's models.
How to choose the right smartphone OS for you
Price vs. OS version
The cost of your contract partly reflects the hardware capabilities and amount of storage on your phone, but you should really judge the value by what the mobile OS offers.
Any current iPhone can be updated to iOS 6 (the latest version of Apple’s mobile operating system) for free, but whether or not you can update an Android phone to the latest 4.1 Jelly Bean version depends on the operator and the device itself.
Samsung’s Galaxy S3 is upgradable, but the cheaper Galaxy Y supports only Gingerbread (Android 2.3). Some budget phones such as the Sony Xperia tipo ships with Android 4.0 Ice Cream Sandwich, but is unlikely to ever get an upgrade to Jelly Bean.
To get the latest BlackBerry OS, you need to either the BlackBerry Z10 or the business-focused Q10 handset.
Windows Phone 7 smartphones can’t be upgraded to the latest Windows Phone 8 OS, but some can be updated to Windows Phone 7.8 which adds a similar home screen. Again, availability of the update depends on the manufacturer and operator.
Let's look at the mobile OSes in turn.
Apple iOS 6
The latest version of Apple's mobile OS which runs on the iPhone, iPad and iPod touch offers the broadest choice of apps of all smartphones and comes with plenty of Apple’s own apps.
The likable Safari web browser supports multiple web pages, but the lack of support for Flash means some websites don't work. Synchronised bookmarks (via iCloud) and the ability to save pages for offline viewing (Reading List) are handy. In-private browsing is supported.
Typing is fairly swift once you master overriding Apple’s autocomplete suggestions. Good note-taking, reminders and calendar apps are provided.
Email support is equally solid. You can easily add multiple email accounts from Outlook to iCloud Mail, Yahoo, Google and Exchange, then designate contacts as VIPs. You can view inboxes separately or show all messages in a single inbox view. Mail is searchable by name or subject via a field at the top of the screen.
Voice search via the Siri digital assistant is largely a gimmick and requires a Wi-Fi connection to use. The ability to view documents sent as attachments is welcome, but they can be saved locally only if you have certain apps installed which support those file types.
iOS 6 has a handy Notification Centre and you'll see notifications appear on the Lock Screen so you don't need to unlock your phone. You can also disable all notifications between preset hours (the Do Not Disturb feature) so you can avoid distractions.
A central Settings app is used to manage almost every element of iOS, with on/off toggling for Bluetooth, roaming, in-app purchasing and third-party app integration. Some parental controls are provided and it's easy to synch and backup using iCloud or iTunes.
You need an Apple ID to buy apps and to manage most elements of your iOS life. Purchases can be viewed or installed on any other iOS device you own (up to five computers can also be registered to your iTunes account at once).
Music, games, TV shows, film rentals and other iTunes purchases can all be deleted to free up space and subsequently downloaded for future viewing. You get 5GB of iCloud storage, but photos, videos and purchases don't count against this. Of course, you can pay for more or use Dropbox, Box.com or other cloud providers.
Apple replaced Google Maps with its own Maps app in iOS 6, but you can still get Google’s superior maps app which also includes Street View. On the iPhone 4S and 5, you get turn-by-turn driving directions and the pretty-but-pointless 3D view in major cities.
Integration with audio hardware is impressive via both Bluetooth and Apple AirPlay wireless streaming (Apple's TV is great for wireless streaming too).
Aside from the sheer number of apps in the App Store, one of the big advantages of iOS is that Apple curates all apps, so rogue installations (and malware) are less likely than with Android.
See also: iOS 6 review
Next page: Google Android