Every phone now offers a choice: a face scan, a fingerprint, or a plain old PIN. They're not interchangeable, each one trades off convenience and security slightly differently, and it's worth knowing which.
Biometrics: fast, and mostly about you
Face and fingerprint unlock rely on something unique to your body, which makes them hard to guess and fast to use. The trade-off: your face and fingerprint can't be changed the way a password can, and in most of Australia, police can compel you to unlock a device with your face or finger far more easily than they can compel you to reveal a PIN.
A password is something you know. A fingerprint is something you are, and you can't change what you are.
A PIN: old-fashioned, and still solid
A PIN, especially a longer one, doesn't have that legal quirk, and it can't be lifted from a photo or a glass surface the way a fingerprint theoretically can. The trade-off is it's slower and more visible to someone watching over your shoulder.
The realistic answer
For most people, biometrics for everyday convenience with a strong PIN as the backup is a perfectly sensible combination, which is exactly how most phones are already set up by default. The setting worth checking isn't which one to use, it's making sure one of them is actually turned on at all.
Check yours is set up properly
Apple and Google both publish official guidance on device unlock and security settings. Find both on the Free Resources page.