GroupMe vs Flock

GroupMe has a built in function to read receipts.

GroupMe has an excellent web client that can be used to send and receive messages and manage groups from the desktop.

Allows sending messages from web services via IFTTT.

It's possible to add location and time with reminders directly in the GroupMe app.

GroupMe has settings that allow muting a single group or turn off all GroupMe notifications from within the app.

GroupMe can set up a custom phone number which allows people without the App to send and receive messages. This makes it easy to add anyone to messaging.

They have apps for Windows, Mac, Chrome, iOS, Android and web interface. And all the chat sessions are always on sync.

It is half the price of Slack and full of nice features like polls, assign to do's, etc.

Unlike its rivals, it not only allows you to receive events, but also allows you to push content to it and receive various user action events.

Moving a team or organization to flock does not require any setup from the company's IT team. At max, what might be required would be to whitelist their domain in case the organization's IT team has gotten external domains blocked. You can simply download Flock and invite others in your organization by using their email ids in order to start collaborating. That's all there is in the name of setup.

Most of its features are free, even video conferences. But also they have a Pro version with unlimited chat history, Active Directory integration among other things.

There is no limit on the number of groups or of group members. Similarly, within a team you can have unlimited members. There is no limit of number of teams too.

Flock is offering an app that is faster than Slack.

For every team, the permissions and restrictions can easily be set over the participating members and the conversations they are having.

Posting messages is more fun with them in addition to emojis.

There are multiple options like slash commands, message buttons, chat buttons, attachment picker etc., where the integrations can surface inside the native app. This greatly eases the discoverability of a integration, making it really easy for the team members to find and use the integrations.