When comparing Messenger vs Hall, the Slant community recommends Hall for most people. In the question“What is the best team chat software?” Hall is ranked 60th while Messenger is ranked 74th. The most important reason people chose Hall is:
There is iOS, Android, Mac, Windows, Linux and web software available.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

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.
Pro Cross-platform desktop, mobile and web
There is iOS, Android, Mac, Windows, Linux and web software available.
Pro Multiple service integrations
Hall integrates with Dropbox, Box, Asana, Trello, Github, Heroku, Jenkins, New Relic, Pivotal Tracker, UserVoice and Zendesk.
Pro Free
Free on on all devices.
Pro Dropbox and Box integration
You can use Dropbox and Box to share files in Hall.
Cons
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.
Con Has gone out of service
But may be integrated into Atlassian's HipChat.
