When comparing Instagram Direct vs Messenger, the Slant community recommends Messenger for most people. In the question“What are the best messaging apps for Android?” Messenger is ranked 21st while Instagram Direct is ranked 47th. The most important reason people chose Messenger is:
Allows communicating with anyone who's a friend on Facebook.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Video & photo messages
Photos have to be cropped to be square.
Pro Filters
That can be applied to photos and videos.
Pro Group messages
With up to 15 people.

Pro Uses Facebook friends to create a contacts list
Allows communicating with anyone who's a friend on Facebook.
Pro Read receipts
Can see who has seen each message in group messages.
Pro Easy to share posts from Facebook
Integration with Facebook makes it easy to share any interesting posts from the Facebook timeline.
Pro Great UI
User interface of the application is clean, intuitive and easy to overview.
Cons
Con Walled garden
Can't communicate with people outside of Instagram.
Con Lack of privacy
Messenger is owned by Facebook. Based on their privacy policy, this means that any information you provide (including messages sent) are used by Facebook to profile you and sell access to your data to advertisers.
Con Lack of end-to-end encryption
Secret (end-to-end encrypted) chats are only supported in one-to-one messages, and are not enabled by default, and the encryption has not been verified independently.
