If I understand it correctly, refusing either one could land you in detention (or jail) - law enforcement officers have a pretty broad ability to detain people

If I understand it correctly, refusing either one could land you in detention (or jail) - law enforcement officers have a pretty broad ability to detain people for lawful investigations (or, what they beleive are lawful investigations). The difference is that you'd be released after refusing a passcode (but possibly having to appear in front of a judge with a lawyer), whereas the court could hold you in contempt (and jail) for refusing biometrics.