There are thousands and thousands of application on android & apple platform for communication purpose but Whatsapp is uncomparable to all . Application markets have same to same copy of whatsapp also but no one hit like whatsapp. I use is from 2.5 years & whatsapp is improved day by day.
Number of group members goes 50 to 250. So whatsapp is changing herself according to peoples recommandation and thoughts. We all are fan of whatsapp.