Like WhatsApp, Viber is free to use and has no advertising model. If they are not making money off me directly i have to wonder how safe my data actually is with this service.

WhatsApp is not free to use. iOS users are charged a flat 99c fee while Android users are charged 1$ a year from the second year onwards.

I do not know how secure Viber is but they have been steadilu acquiring good user base. If I was Viber, I would cash on this opportunity to write a blog or advertise their security models.

I' ve been using WhatsApp well over a year on Android. I got a free renewal in june. Never paid a cent.

Sure, you may have but are you the exception or the rule?

I sometimes use Gryphn to send super secure messages like giving a client my bank account #.

But is it more secure?

No way to know. The way I see it I have two otions in te worst case scenario

Option1 - Use an insecure paid app Option2 - Use an insecure free app

I am not sure about you but I will choose Option2 gien the constraints and restrict my use to communications which have no privacy problems.