Security

This is perhaps the most important factor when we consider social apps and services. Since we are readily sharing information with other people, we want to be sure that this information is not accessible to any unwanted individuals.

WhatsApp has been a frequent victim of security breaches ever since its launch. According to Wikipedia, WhatsApp messages were initially sent and delivered in plain text; although the issue was addressed later. Some other reports also suggested that you could change the status of a WhatsApp contact by just having access to his / her phone number. Though most of these security holes have been patched (reportedly), WhatsApp continues to be vulnerable. In fact, some people have claimed that it is possible to even obtain the encryption key used for sending and receiving messages, making it possible to eavesdrop on conversations and easily fake your authentication as another user.

On the other hand, BBM is well known for its industry grade security from the BlackBerry Team. BBM is more reliable as messages are fully encrypted and only the sender and receiver have the ability to fully decrypt messages.

So, in terms of security, BlackBerry takes the lead.