Face ID is at least as secure as Touch ID, but it does have its drawbacks. If you have an identical twin, for example, they will probably be able to fool it. And if someone gets ahold of your phone and manages to point it at your face, that might unlock it (provided you turn your attention toward it).
Apple has safeguards in place, just as it did with Touch ID: If Face ID tries to authenticate on someone else's face and fails several times, it will disable and require your passcode.
Still, there may be times when you feel that you don't want anyone to be able to use Face ID to get into your phone. Fortunately, it's quite easy to temporarily disable it. It's fast and discreet.
