I definitely agree with the Google Drive app as well as Google Maps. As a matter of fact, take a look at all of the Google apps out there. I have most of them and I love it.
I use Microsoft services on my device. Other than Search (actually looking for stuff, I don't really use Google Now), Maps, and YouTube I have no need for Google's services - and no matter what major platform I move to I know I will be supported. Google really sort of ties you down to Android or iOS pretty much these days. I'm not content with only two options, as I am not really a fan of no particular mobile OS, and use what I feel like using.
I have been through the whole "change from one set of services to another" when you move platforms and find out the services you were using are poorly supported there... That trouble is not worth it.
That being said, at least on my Samsung device, there are clear advantages to using Microsoft's services over Google's: Outlook.com has Tasks support via EAS - Google Tasks require 3rd party applications and those apps aren't as good as the built-in support in Samsung's Calendar app. Skype works over Cellular and supports file transfer (any type of file i.e. a Word document or ZIP file). OneNote Mobile poops all over Google Keep, especially since the latest update...
Many reasons, but being able to use them flawlessly with desktop applications as well as migrate from mobile platform to platform without a serious degradation in user experience is also a big win for me going from Google to Microsoft services.
Android doesn't = Google to me. Just like iOS doesn't = iCloud because when I used iOS I didn't use any of their PIM services, Photo Stream, or anything like that. That stuff is not portable and I was using 3 mobile OSes basically all the time every day back then (Windows Phone, Android, iOS) on 3 devices I carried everywhere.