In one, you intentionally give false information and lead the government believe you in good faith complied. In the other, the data is inaccessible and the government is aware it is inaccessible. They can then evaluate risk and seize the device or take some other action from that knowledge. IANAL and I don't play one on TV.

ETA: To complete the threat analysis, and if they seize two devices, one with a password protected key and a LUKS volume without headers? I'll take LUKS.