If you listen to both of them without autotune, Ariana Grande has a better singing voice without autotune when compared to Katy Perry without autotune. Ariana Grande has better high notes, And overall can sing better without autotune. You can look for yourself, Just look up both of them with no autotune.
SHE IS A lot better because she has song lyrics that make more sense and she is also prettier than Ariana Grande. I love Katy Perry. So yeah that is why I think that katy perry is way better than Ariana grande at singing and making up song lyirics. Go katy