Pro Good built-in contacts
In addition to showing contact information, the People section of Outlook can show all conversations you've had with a person. Moreover, if you're looking for someone that's not in your contact's list, but is in your company's or school's directory, Outlook can pull that information through integration with Global Address List (GAL).
Pro Easy authentication via Microsoft's own authentication app/service
Similar service to what's offered by Salesforce, Google, Apple, Yahoo, and other larger/more sophisticated firms with large platforms available for iOS. Safer/more secure than typing password for login, and easier. Credentials stored in the keychain.
Pro Integrates with cloud storage services
Microsoft Outlook comes with built-in cloud storage browser allowing you to attach files directly from services such as Dropbox, Box, Google Drive or OneDrive to emails and directly open attached files without the need for the main cloud storage app.
Pro Quick swipe features
Microsoft Outlook comes with quick swipe features where users can quickly swipe the thread either from left (to schedule) or right (to delete or archive). Additionally, users can also customize the swipe actions to, for example, set swipe from left to archive or swipe from right to delete.
Pro Helps prioritize email
The app will automatically attempt to figure out which emails are important to you and surface those. The priority emails will show up in your inbox in a tab called Focused, with other emails in a tab called Other. It aims to separate spam and promotional emails from the important emails.
Con Doesn't follow security guidelines
The app stores user information and credentials on outside servers which is a violation of ActiveSync password requirement policies. These security concerns have been enough of an issue that European Parliament has banned its members from using the app out of fear that it might lead to leaking sensitive information.