The iPhone 5s, with Office Mobile and an app of your choosing to allow you to attach documents to business emails of which there are several to choose from in the App Store, is a fantastic device. Especially since there are so many businesses and professions that require highly specialised apps which are found in the App Store.
Aside from that, it is perfectly managed in Enterprise via Good or Mobile Iron or some such MDM. There are less vulnerabilities in iOS than there are in Android, which is why so many businesses use iPhones for their mobile needs.