When comparing WhatsApp vs Rocket.Chat, the Slant community recommends Rocket.Chat for most people. In the question“What is the best team chat software?” Rocket.Chat is ranked 7th while WhatsApp is ranked 54th. The most important reason people chose Rocket.Chat is:
Rocket.Chat is available for free. It's licensed under the MIT license with source code available on [GitHub](https://github.com/RocketChat/Rocket.Chat).
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Straightforward interface
The interface is very simple, fast and easy to use. You can start using it as soon as the app has been downloaded - it does not require setting anything up or registering. You can communicate with anyone in your contacts list that also uses WhatsApp. Includes useful features like seeing when a contact is currently available or typing.
Pro Widely used
WhatsApp reported 1.5 billion users in 2018. Your friends are most likely already using WhatsApp, so it's easy to get setup.
Pro Effortlessly builds your contacts by using your phone number as identification
WhatsApp will automatically find all of your contacts currently using Whatsapp and add them to your contacts. This makes it really easy to setup and given that it's the most popular messaging app it's likely that a lot of your contacts are already using it.
Pro Message mirroring on web app
WhatsApp can be used from the desktop via Chrome, Firefox and Opera browsers. Accessing it requires using the Android app to scan the QR code that's presented on web.whatsapp.com.
Pro Signal protocol
Whatsapp uses the state-of-the-art Signal protocol that ensure strong end-to-end encryption.
Pro One-on-one texts can be encrypted
WhatsApp has implemented end to end encryption for messages sent on it's service. Even WhatsApp has no way to read a users messages.
Pro Free and open source
Rocket.Chat is available for free. It's licensed under the MIT license with source code available on GitHub.
Pro Native apps for all major desktop and mobile platforms
Rocket.Chat has native apps for macOS, Windows, Linux, iOS and Android.
Pro Supports a wide variety of authentication methods
In addition to the usual email / username + password combination, Rocket.Chat supports authenticating via Facebook, Github, Gitlab, Google, Linkedin, Meteor and Twitter accounts.
Pro Understands markdown better than Slack does.
Links work properly, for instance, with square brackets followed by parentheses.
Pro Very active and helpful community
Pro Video conferencing support
Rocket.Chat supports video calls.
Cons
Con Shares meta data with Facebook
WhatsApp shares your messaging meta data with Facebook if you do not opt-out in the settings. If you use the same phone number for WhatsApp and Facebook, the profiles can easily be linked.
See https://www.whatsapp.com/faq/en/general/26000016
Con Tied to carrier phone number
WhatsApp cannot be used by people without a smart phone with an active cell plan. If your phone is lost or damaged, or if your phone number changes, you cannot get messages sent by friends without them updating your phone number. You cannot send message to them until you are able to get SMS messages at your phone number.

Con Proprietary
Not open source.
Con Hard to migrate history cross platform
Migrating your chat history from Android to iOS or the other way around is not so simple. In some cases it requires a 3rd party app and in some the only way is to migrate specific chats one by one.
Con Web interface uses message mirroring
To use your computer to send messages your phone must be on with a consistent data connection.
Con Single device
You cannot use the same WhatsApp account on multiple devices (e.g. a tablet, a PC and a cellphone). The account is tied to the device with the specific cellphone number. Chat history is deleted when you sign in to a new account, unless you have created a backup.
Con No cloud sync
Messages are not stored on WhatsApp server for privacy and security reasons.
Con Limitation on shareable file sizes
WhatsApp now allows users to share files of any type, but there is still a 16 MB size limit.
Con Developer support is non-existent
Can't even create a clean Ubuntu VM with a working developer install. Unresolved dependencies; fails to build. Docs are terrible; actual devs don't respond to questions; error messages are near-opaque. DO NOT RECOMMEND.
Con Web client loses images
In chat rooms with images, before very long, images start to become empty boxes. Useless to pass around visual information
Con No theme customization
Con No chat audit for enterprise
Con Poor security implementations / protocols
Con Centralized
Con iOS app is poorly made
The iOS application is not native, being just a browser container. This means that the UX is quite poor, slow, buttons unresponsive. At this moment they do not provide a decent experience.
Con Android app is poorly made
The Android application is just a badly wrapped web-view which does not perform well and has no form of offline caching whatsoever.
Con Privacy settings are absent
Privacy settings for the server are absent, for instance, you don't have the ability to disable registrations, there's no way to control access to the chat.
Con Features not available out of the box
Con No web browser support
Con Email required for registration
Con No way to block new registrations
Without the ability to disable registrations, there's no way to control access to the chat.
