FaceID uses an Infrared point cloud scanner that illuminates your face with invisible-to-humans light. It works fine in the dark.i don’t know. I heard FaceId wasn’t working in the dark. Like if you are watching something in your bed, or going outdoor in the night. but maybe it’s working. I only know that Touch ID work anytime and anywhere.
As a rebuttal, TouchID does not always work. When wearing gloves, in cold areas it is not the best option.
My parents own SE2/3 with TouchID and it had a hard time detecting their fingerprints! Oh what it is to be young!