Android's Calendar displays calendar items in your linked accounts. Like Android's Gmail and Contacts, Android's calendar shows all of your Google account calendar items. The Android Outlook app works much like the W10 version in that mail, contacts, and calendar are integrated. I find that I use Outlook.com to organize family events since everyone in my immediate family has Windows 10 and therefore an Outlook.com account. I can easily add events and appointments to my Windows 10 Calendar app without having to open up a browser and going to my Google calendar.
In my case, I use Outlook calendar for family events and appointments and Google calendar for everything else. You can share your calendar with others in Outlook.com by sending a sharing invitation email. Conversely, you can ask others to share their Google calendars with you by sending a sharing request email. For family, this allows you to easily display shared calendars in the Windows 10 calendar app. For example, if your university-age kids have shared their Outlook.com calendars with you and they've added their class schedules, you can tell at a glance when they're available to Skype.