FaceID will not likely work if you change your face (e.g. black eye, swollen whatever, face cut, aging, you name it) but your fingerprints NEVER change (short of burning them off with acid). Previous implementations of facial ID have been fooled by pictures attached to 3D CGI images even.
Apple should really offer a CHOICE of what to use in the future, although frankly, the cops (or even muggers or others) can force you to put your face in front of a camera and unlock your phone OR push your finger to the screen quite easily. The ONLY reasonably "safe" security is a CODE and the ONLY method protected by the Constitution in the US (thus far) against self-incrimination. And if you think only criminals need worry about that, check out how many prisoners (including death row) have been exonerated by DNA in recent years. You can't trust the system to do right by you. It's both flawed and corrupt. I'll stick with a pass code regardless of what phone I use. If a phone eventually comes out without a code option, no sale.