Deterrence is always preferable. Clear monitoring may stop crimes in addition to capturing wanton disregard. A disguised bathroom cam is clearly designed to capture illegal footage. It isn’t a deterrent to crime, it’s a tool to commit it. Spy cams in general are sleazy and disgusting.
Even a nanny cam, despite the clearly just intentions, allow a crime to happen more so than clear security cameras and can be used for less lawful things due to their design.