If you want your users to have the best Office 365 experience then Outlook for iOS and Android is the best way to go. We are an 80,000+ company and are just mid way through migrating our users to Intune (from AirWatch). We have set Outlook as the default client and the majority of our users love it. They key is to show and educate users on why Outlook is so much better than the fragmented experience they have with the native Mail and Calendar apps.
Once they get over the initial bump users are love all the new capability that Outlook brings. Just the ability to book rooms and having Microsoft's AI and machine learning showing you the available rooms based on the people in the invite is a crowd winner.
Add in SSO with Microsoft Edge to the company intranet and they are sold.