Why some might prefer finger vein to fingerprint

'Finger vein recognition system' promises security (Times of India)

[...C]opying and hacking fingerprints to breach security can be stopped by mapping people's veins to verify their identity. This model can be used to make up for errors and loopholes in the biometric system, where finger prints can be copied easily.

"Using the blueprint of our veins, areas like credit card security and other time attendance systems can be strengthened.

Even shorter answer: there's no latency.