PROS: The innovative knock knock feature allows you to see who is calling before you answer, Extremely simple interface to use, Specialized to work specifically on your mobile phone or tablet so there's nothing you don't need and everything is directed to one purpose: making video calls
CONS: No voice only option, No compelling reason for IOS users to switch to Duo from Facetime for calling other iOS users, Both users need to have Duo installed to start the voice call
PROS: Similar functions and capabilities when compared to larger providers such as Skype., Competitive international calling rates.
CONS: The calling rates are not guaranteed and they will fluctuate from time to time. , As this is a less powerful software platform you may experience reduced signal strength and lagging call times on occasion.