Biometric phone security is only secure until a judge or police officer compels you to unlock your phone; and legally you must comply, because your face or finger aren't speech. However, if you use a passphrase, (at least in the US and other countries with string freedom of speech laws) you can't be legally compelled to unlock the phone, as that would impinge on freedom of speech.
I never use biometrics to unlock my phone or computer for that reason.