Signal vs Flock

Signal uses an advanced end to end encryption protocol that provides privacy for every message every time.

Signal is free and open source software, enabling anyone to verify its security by auditing the code. It's the only private messenger that uses open source, peer-reviewed cryptographic protocols to keep your messages safe.

Signal Desktop can be used on multiple devices and has most features of the Android version, although it still requires you to register with your phone.

Signal supports: emoji, pictures, videos, audio, contacts, any location and GIF.

Allows you to "send: messages to yourself and sync to desktop so you can use Signal as a kind of encrypted Pushbullet alternative

You can easily view all media shared in the chat without scrolling back to when it was shared.

The sender credentials can be encrypted with the rest of the message, leaving only the recipient address readable by the Signal server. Even if Signal wanted they couldn't see who is talking with who by this mean.

Unlike most messenger apps, Signal works reliably in all countries by securely circumventing internet censorship.

Edward Snowden uses this messenger and recommends it to everyone who is concerned about his privacy.

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.