Both tests are questionable, but one more then the other: A psychopath might not necessarily be as uncomfortable with what makes them into a psychopath. An actual narcissist on the other hand is a lot more likely to answer whichever answer depicts them in the best way possible, and in the case of someone who is knowingly taking a narcissism test, the answer is the most non narcissistic traits.
And the questions are rather transparent:
For comparison with professional diagnostics, I've had the experience of a psychiatrist testing me for various possible conditions, NPD among them, and the specific ways in which she tested for NPD mostly consist of testing my reactions to criticism, blame, self evaluation about past failures, an my interpretation of the roles of others in my relationships, all without telling me what she's doing until the finale summary of everything she was able to find.