Recs.
Updated
SpecsUpdate
Pros
Pro Straightforward interface
The interface is very simple, fast and easy to use. WhatsApp does a great job of focusing on the basics behind messaging. The app is simple to use, fast & very polished. 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 End to end encryption in all messages and calls based on Signal protocol
Pro Effortlessly builds your contacts
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.
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 Hard data collection
A lot of telemetry is collected as part of what is called "meta-data" or "anonymous data". It is only anonymous as in knowing where you live, where you work, where were you last weekend, your sleeping habits, your most opened conversations, all your contact addresses and how they address you, and much more - but not knowing you personally.
Recommendations
Comments
Flagged Pros + Cons
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 Widely used
WhatsApp reported 800 million users in April, 2015. Your friends are most likely already using WhatsApp, so it's easy to get setup. Also it's the overall highest rated messaging app on the play store.
Out of Date Pros + Cons
Con Account is limited to one 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. That also means that there's no sync since it doesn't keep conversations when switching operating systems or devices.
Con Doesn't support file sharing
It doesn't let you share files, only pics, vids or music.