The point of a safe is to make it difficult for anyone to access the content without your approval. Given time and the right tools, I would argue that any safe can be compromised. For residential safes you just want to make it take longer than a criminal is willing to spend in your home.
Mechanical locks have several advantages.
- they don't require batteries
- they are more durable (moving a safe is very difficult, and you may bump into a wall trying to squeeze through a doorway)
- they will likely last longer than the electronics
- harder to sabotage (you could be locked out by someone breaking a keypad)
I have never had a battery die on me, but I have heard you just pop in a new one and your code should work as normal, it is a small inconvenience unless your in an emergency situation.
I can't really speak to biometrics, but I think they are generally more expensive and have the same And several additional disadvantages to the standard electric keypad.
Viv