Katy Perry times from a different angle ...

Those who have bought this album will be surprised first - because Katy has tried on the album 'PRISM' something new. The third album is clearly 'different' - more pop than previous. Does not necessarily mean the Prism is a bad album!
Personally, I think the new album 'Prism' succeeded. It may not be completely round album but still very good.
And do not compare with the other two albums.

Should listen Unconditional you look:
Roar, Legendary Lovers, Walking on Air, Unconditionally, Dark Horse, Love me, this moment, Double Rainbow, By The Grace Of God & it takes tow
These are the best songs on the album.