There’s a lot more to a smartphone than hardware. / Credit: Shutterstock

The best business smartphones have sharp displays, high-quality builds and long battery life. But there's a lot more to a smartphone than hardware. Ultimately, what makes a phone great for business is the software it runs on. There are three major operating systems available on smartphones today: iOS from Apple, Android from Google and Windows Phone from Microsoft. Each offers a distinctive spin on the smartphone experience – but which one will make you most productive in the long run?

When it comes to smartphone satisfaction, ultimately it's all about the apps. All three major mobile operating systems can cover your basic productivity needs, but there are big differences when it comes to the number and variety of apps available.

Android: In terms of sheer scope, the Android app store – dubbed the Google Play store – rivals the iOS App Store, with more than 1 million apps available. That includes everything a business user needs for taking notes, balancing a budget or viewing and editing documents. There are some small discrepancies; apps sometimes debut on iOS first, and iOS retains some notable exclusives. For the most part, however, the overall quality and availability of apps on Android and iOS is about equal.

iOS:It's hard to top Apple's App Store when it comes to app support and availability. It can match almost every offering and Android and Windows Phone, and some popular business software, such as the Kashoo accounting app, are exclusive to iOS.

Windows Phone: The Windows Phone Store is perhaps best known for having a much smaller selection of apps than competing platforms – about 100,000, compared to selections of more than 1 million on Android and iOS. That doesn't mean there isn't a Windows phone app to cover all the needs of business users. If you're looking for a good calendar app, or a popular productivity app such as Evernote, you're likely to find it. The Windows Phone Store is also growing fast. But for now, if you're loyal to a particular mobile app or service, make sure it's available on Windows Phone before committing to the platform.

Baked into each mobile OS are unique features that will give business users a boost.

Android: Android offers Google Now, an intelligent personal assistant that can help business users stay on track and never miss a call or meeting. The service works by monitoring your activity within the Google ecosystem and pushing relevant notifications to you as they're detected. In practice, the service can notify you of traffic delays, weather, upcoming appointments and much more.

iOS: The iWork for iOS apps are fully integrated with Apple's desktop iWork applications, letting users view and edit documents seamlessly on multiple devices. The latest iteration of iOS also adds features such as AirDrop, which lets users share files with a single tap, as well as a revamped email app with the ability to add auto-sorting mailboxes and view PDF annotations.

Windows Phone: Windows Phone is the only mobile platform with Live Tiles, which update in real time to display relevant information right on your home screen, ensuring you never miss a message or meeting. The platform's biggest draw for business users, however, is its full integration with Microsoft Office.

Security is a top concern for business users who handle sensitive information, such as private client data, on their mobile device.

Android: It's easy to side-load an unapproved app on an Android phone by downloading and installing the application from a source other than the Google Play store. Google is also more relaxed about which apps it allows to appear in its app store, and the fragmented Android landscape makes it trickier to patch vulnerabilities. In most cases, however, your files should be secure if you stick to apps from trusted sources only.

iOS: Apple's iOS is a highly secure mobile operating system. It's virtually impossible to install apps from unofficial sources -- at least without a concerted effort– and all apps are reviewed and approved before they become available to download in the App store.

Windows Phone: On the security front, the Windows Phone platform is comparable to iOS. All apps are reviewed and approved by Microsoft, and unlike on Android there's no need to consider dedicated anti-virus and anti-malware software.

Each of the three major platforms runs only on specific smartphone models.

iOS: It’s easy to pick an iOS device, because the operating system is found only on the iPhone. Currently, Apple sells just three version of the iPhone: the flagship iPhone 5S, the fastest and most feature-packed model; the midrange iPhone 5C, which comes in a variety of colorful cases; and the lower-end iPhone 4S. Power users can opt for the 5S, which packs a fingerprint scanner for added security in addition to powerful hardware; meanwhile, the 4S is still speedy enough to satisfy a business user on a budget.

Android: What the Android platform offers that competitors do not is a huge selection of unique phones. This is a big plus for power users who wish to select a smartphone with a very specific feature set, but it can be tricky to navigate through dozens of mediocre devices. Consider sticking to top-tier phones such as Samsung's Galaxy Note 3, Motorola's Moto X or LG's G2.

Windows Phone: Windows Phone comes on just a handful of smartphone models. The most popular are the phones in the colorful Nokia line from Nokia, but several other models are available from manufacturers, including HTC and Samsung. Business users who want a well-rounded phone can consider the Lumia 925, while those who want a big screen can check out the Lumia 1520.

Ultimately, Android, iOS and Windows Phone have a lot in common, and each provides a solid platform for business users to run the apps they need. But each also has one-of-a-kind, productivity-boosting features. Windows Phone boasts a user-friendly interface and handy features such as Live Tiles. Android is the most customizable, making it a good fit for power users. Meanwhile, iOS offers a simple but powerful interface that's backed up by the best overall selection of apps.