For Katy, I'd say either California Gurls or Roar. California Gurls sounded exactly like a song that was huge already (risk of over exposure, people getting sick of hearing it since they'd already heard Tik Tok for so long), and Roar is really risky because the lyrics are so poorly written (cliche after cliche) and the message isn't relatable (who "roars"?).
The reach
Roar is probably the safest radio single of the last 2 years..
