Zulip is great. After using it for a while, I no longer want to use anything else.
The light-weight topics make a lot of sense. You can quickly discuss a topic and then forget about it.
With Slack, you'll need to create a new channel, invite people into it, it's just much more overhead so you end up discussing in the main channel.
A huge issue with Slack, for me, is catching up with busy channels. You have to read all of it since you miss discussions on topics you're interested in. Zulip has a great solution to this issue.
I'm also impressed with how high-quality it is. They even have Nagios checks and everything. It has many features you miss in other products like Rocket Chat (full text search. administrative tools, ...).
The light-weight topics make a lot of sense. You can quickly discuss a topic and then forget about it.
With Slack, you'll need to create a new channel, invite people into it, it's just much more overhead so you end up discussing in the main channel.
A huge issue with Slack, for me, is catching up with busy channels. You have to read all of it since you miss discussions on topics you're interested in. Zulip has a great solution to this issue.
I'm also impressed with how high-quality it is. They even have Nagios checks and everything. It has many features you miss in other products like Rocket Chat (full text search. administrative tools, ...).
Edit: relevant comment from another thread. https://news.ycombinator.com/item?id=10281065