When comparing Stride (previously HipChat) vs Zulip, the Slant community recommends Stride (previously HipChat) for most people. In the question“What are the best Skype alternatives?” Stride (previously HipChat) is ranked 22nd while Zulip is ranked 24th. The most important reason people chose Stride (previously HipChat) is:
You can access HipChat from pretty much every common platform. HipChat even allows chatting via SMS.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Available on Web, Mac, Windows, Linux, iOS, Android
You can access HipChat from pretty much every common platform. HipChat even allows chatting via SMS.
Pro Powerful @mentions
You can ping people to get their attention even if they are not online by @mentioning them. Depending on how the person has set their account up it can be by notifications via in-app sounds, visual alerts, and even email, SMS, or mobile app push notifications.
Pro Huge list of integrations
Including Asana, Github, Zendesk, WordPress, MongoDB, TeamCity, JIRA, Confluence, PowerShell and more that 40 others.

Pro Cheap
Free with unlimited users, $2/user/month for voice + video calls, screencasts, full history retention and management. (Even enterprise feature like SAML)
Pro Simple, easy to use
An intuitive, easy to overview interface listing both online and offline users.
Pro Embeds files
Things like photos get automatically embedded in the chat thread once you upload them.
Pro Guest access
You can invite people to join conversations even if they don't have a HipChat account. HipChat will generate a link to share and the guest will only need to enter their name to join the conversation.
Pro Desktop client
HipChat has an optional desktop client powered by Adobe AIR.
Pro Good audio and video support
HipChat audio and video works on mobile platforms and web browsers.

Pro "Rooms" for persistent group chat
Participate and keep tabs on ongoing discussions on particular topics or amongst certain groups of people.
Pro Self-Hosting available
If you are worried about third-parties getting access to your data you should consider self-hosting. With self-hosting you are in control over where your data is stored, who has access to it. You will also not be vulnerable to exploits of a third-party provider.
Pro Plentiful GIFs and custom Emoticons
Pro Syntax coloring
Pasted code can be colored based on syntax.
Pro Will be updated to have more functions in the future
A big company with experience will bring in more options like Google Apps One Time Login.
Pro Reliability has been great
Pro Powerful command system
E.g. part, away, all, here etc.
Pro Helps keep track of different conversations
Instead of rooms or channels Zulip is built around topics. This allows you to have multiple conversations at the same time without conversations interfering with each another. It also allows you to reference conversations without clutter.
Pro Free and open source software
Zulip is free and open source under the Apache 2.0 license.
Pro Easy asynchronous conversations
Its threaded model helps people working in different timezone's communicate effectively.
Pro Apps for every platform
Pro Hosted or on-premise
With data export tools so you can migrate.
Pro Intuitive interface
I struggled with Slack, never finding the settings I like to adjust. With Zulip never had such issues.
Cons
Con Will be discontinued Feb 2019
Slack acquired Stride / Hip Chat. Both Stride and Hip Chat will cease to exist. Sad since they were quite usable.
Con Prioprietary (non-free/libre)
Con Reliability of service has been weak
The reliability of the hosted HipChat service, particularly in the early days of version 4.x, has not been a strong suit.

Con Free plan has limited storage
Free plan comes with 5GB of storage, where as paid plan has "Unlimited".
Con Only one-on-one video calls in free version
There is no option for multi-user conference calls.

Con No emoji
There's no emoji support. Instead there are some strange custom emoticons which only make sense for people steeped in internet subculture and never get updated.
Con API calls are limited even on paid plan to 500 calls in 5min by default
This will force you to contact them when you need more calls.
Con Non-synced notifications
Messages read on one client don't sync their status to another client.
Con No End-to-End Encryption
Not even for private one-to-one messages, let along group chats.
Con Takes some getting used to
As most chat software uses the concept of channels or rooms, getting in the habit of splitting each topic off in a separate category can require some getting used to and discipline.
