If you want or need to use Microsoft Office and services, you'll want to use them on iPhone.

We've already covered how iPhone and iOS provide not only a great Apple app experience, but a great Google and Microsoft app experience as well. Because of the iPhone's popularity and uniformity of platform, it's not only easy to develop for iOS, it's hard not to. That may be why a lot of people who prefer Google or Microsoft services also prefer switching to iPhone to use them on Apple's hardware. It's not just Apple enthusiasts who say so either. Longtime Microsoft pundit, Paul Thurrott:

And if you are a Microsoft guy, there are good reasons to choose iPhone over Android … and even over Windows Phone. Microsoft mobile apps generally appear on iPhone before they do so elsewhere, and certain Microsoft mobile apps are only available on iPhone, at least for now. In several cases, you will see finished Microsoft apps appear on iPhone, whereas Android receives a rougher preview release instead. In many ways, iPhone—or iOS more generally—is the place to be if you're interested in Microsoft's mobile solutions.

Paul has a great rundown of all the Microsoft apps and services you can get on your iPhone, often before Android or even Windows Phone, and sometimes even in a more finished, polished, and feature-complete state.

Time to switch!

It should also be noted that if, for some reason, you and your company decides you no longer want to use Microsoft apps or services, you can easily switch to Apple's or Google's, something you can't do on Windows Phone, and something you can only do the latter of on Android.

That's one of the iPhone's biggest strengths — it enjoys first-class support from everyone else — and one of the biggest reasons to switch.