Video: Hipchat vs Slack

Group chat and video chat built for teams. Share ideas, code, and files with your team in real time. Rooms are perfect for individual projects, teams, or entire departments. You can also hop into a 1-to-1 chat with a coworker anytime. Connect your team and build genuine consensus with face-to-face video chat and real-time screen sharing. The next best thing to right next to you. HipChat free open-source (self-hosted) alternatives are: Mattermost, Rocket.Chat, Zulip
Slack brings all your communication together in one place. It's real-time messaging, archiving and search for modern teams. Create open channels for the projects, groups and topics that the whole team shares. Slack searches whole conversations, not just individual messages, so you can find what you’re looking for no matter who said what or when they said it. Slack free open-source (self-hosted) alternatives are: Mattermost, Rocket.Chat, Zulip
Face to face in the news:

2015 - Slack adds emails to channels to stand out over HipChat

Email remains ubiquitous and is quite useful for getting updates from pretty much every service on the Internet. That's why Slack is launching a new feature: all teams on the Standard or Plus plans can have email directed into Slack channels. If you don’t set this integration up correctly, your channels could turn into a clogged up shithole, so be sure to think about what emails you want to bring in and where you want them to be posted. Getting support tickets dropped right into a support channel means that your company can move into action faster. While you most certainly can’t reply to the email from within Slack, the alert alone is extremely valuable. What Slack is helping to kill is internal email, which is the bane of everyone’s existence at work.