Deep vein scan (typically of the palm) is the only biometric that I would find acceptable from a privacy standpoint. It can't be "stolen" or "lifted", it is not visible from a reasonable distance, it can't be easily scanned without the user's consent. It requires being "alive". It is reliable and simple to acquire. I have used it and seen it in action... very impressive.
Fingerprints are horribly abused and left everywhere and can't be read through gloves. Easily copied and fooled.
DNA is extremely expensive, extremely slow, has severe privacy implications, and is left everywhere.
Facial recognition is not extremely accurate, is often slow, and is the WORST biometric from a privacy standpoint.
Retina scan is complex and probably the most expensive besides DNA.
Finger spread biometric is inaccurate and insecure (can be obtained from a distance via