It is one of the best messaging apps and reason being it is simple and efficient.One of the main reason for using this apps is that they don’t sell ads which are quite annoying in other apps .
Whatsaap calling function is not the best on mobile data but if both the devices is connected to a stronger network like WiFi it is great & prefer calling as it is cost free.
Whatsaap features like who read your message in a group and to whom it’s not yet delivery make it better and other regular updates, simple and user friendly GUI make is best. Would recommend everyone to give a try.