There are many biometrics to choose from when implementing a biometric security system. Biometrics can be ranged according to their accuracy and user friendliness. This in turn depends on the environment they will be used in. For example, it would be a bad idea to use a voice biometric in a noisy environment, or a face biometric in a badly lit environment. Another important aspect is cost.
Fingerprint is quite resilient to environmental conditions, but requires special sensors.
This is in sharp contrast to face and voice biometrics, which can use standard sound cards and cameras for biometric input. If more than one biometric is installed, the biometrics can be configured to operate together. The end result is a more secure system. For example, if fingerprint and face biometrics have been installed, the system can monitor camera input and fingerprint sensor input simultaneously to verify both face and fingerprint with a minimum of user interaction. The end result is maximum security and user friendliness.