I really don't like either group. I have a personal bias against 1D because I'm a kpop fan, but they do have a song or two that I listen to when it plays on the radio. As for Justin Beiber, I have nothing against him. I like some of his songs, but I'm not really a fan. So I'd say Justin.
Both! Most people (well, girls) love one and hate the other. I like them both! Not obsessed, but I'm a fan. To be honest though, I'm more a fan of 1D for their personalities than anything else! But I really like Justin Bieber's music, especially from his most recent album, I'm not gonna lie. Just how I feel!