Google values iPhone owners so much they make sure most of their apps run on iOS, and that can be a big advantage.
The apps that Google has released for the iPhone include YouTube, Google Maps, Gmail, Hangouts, Google+, Google Authenticator, Chrome, Google Search, Google Drive, Google Play Music, and more. Having them all on the App Store makes it easier for Android owners to switch to iPhone.
The pros and cons of deep integration
The most often cited advantage for using Google apps on Android is the integration. Google Play, for better or for worse, has become one half the sandwich that makes up almost all Android phones outside of China. That means Google apps go deep into the system and allows for everything from Google Now predictions to seamless intercommunications.
Yet every advantage comes with it an equal and opposite disadvantage. To achieve all that integration, you have to be signed into Google everywhere — from the Google Play store to Gmail to Google Maps to Google Calendar to YouTube to Chrome and on and one. Google gets to know what you're downloading, the contents of your email, where you are, who and when your appointments are with, what you're watching, and most everywhere you're browsing.
Again, many people won't care. For them the quality and "free" price of the services more than make up for the attention and data required as payment. For others, however, attention and data is far more valuable than money, and price we're not always willing to pay.
The value of disintegration
On the iPhone, if you want to use Gmail, Google still gets your communications. Same with Google Calendar and appointments. There are just some things for which you need an account. There are alternatives, like iCloud, Microsoft, and Yahoo!, but if you're all in on Google, there's no way to avoid being all in with Google. Same with Google+, because social network.
Other services, however, you can use perfectly well on iOS without being logged into Google. They don't make it easy, obviously, and they withhold some conveniences to try and incentive logging in, but you can do it. You can watch YouTube videos without being logged in. You can use Google Maps without being logged in. You can even use Chrome without being logged in.
It may not mean much, there may be a hundred other ways to track you and companies doing the tracking, but if you're sensitive about Google in general, yet still want or need to use its services, it may mean something to you.
If it ever gets to the point where you decide Google's interests and yours no longer align enough to use its services, even if they're free, then the iPhone also makes it easy to switch to alternatives. Vimeo, Apple Maps, and Safari are just a few of the options available. Almost everyone makes app for iOS, so you can choose whoever you want. If Docs becomes an issue for you, there's Microsoft Office and Apple iWork. If Hangouts starts to creep you out, there's iMessage, Skype, Whatsapp, LINE, even BBM.
Google offers terrific services for millions upon millions of people, but what's even more terrific is having a choice in whether you use them or not. Even the choice to flip back and forth between using them and not without having to also flip phones just to do it.
Time to switch!
Privacy is an increasingly important issue. Apple has made privacy, along with security, a front-facing feature from the top down. They want it to be a competitive advantage, and that's great for customers who value it as a feature. If you want alternatives to Google apps, or even if you want to use some of Google's apps without being logged into Google, the iPhone is a great way to do it. And it's just one of the benefits you get by making the switch.