I'm a bit surprised with all the backlash against Frank here, but after seeing him on the Grammys I'm inclined to agree, at least with his live vocals. That isn't to say I think he's anywhere near a bad vocalist, but he's not as mind-blowingly adept as all the hype surrounding him has led us to believe.
Never been a fan of Bieber's vocals either. I can't really say more on that since I've only seen less than a handful of his live performances.
Both, bieber is just awful and Frank doesn't actually sing, he just talks throughout his songs, and the videos posted here to prove he's a good singer shows his limited range and flat voice and that last note is dreadful.