There aren't any pros besides them lying to you making you feel like you're the liar...
Inconvénients
They make you feel like a liar with a false positive hair follicle test then they cut you off and don't even return any of your calls or give you a chance to prove yourself. The recruiter was really my friend until those results came in and then every time I got to try to talk to him to prove that they were wrong never even returned my call or answer the email