Well, they both try to take their public images as far as they can, but as far as singing talent goes, Lady Gaga is better. I mean, she has a pretty good voice, while Katy Perry has an annoying voice.
Katy Perry in most definitely. At least we recognize her every time we see her, unlike Lady Gaga. Also, her music is way more appealing to the general public because of its "op" feel.
I find Lady GaGa's music fascinating and artistic. I enjoy analyzing her lyrics, though they offend my delicate sensibilities from time to time. Also, Poker Face is very danceable.
Katy Perry... I hate Katy Perry with a burning passion. Even if I hated Lady GaGa, I doubt I'd hate her more than Katy Perry.