Katy Perry has zero talent, have you guys not watched any of her "live" performances on Youtube? She can't hold a note or stay in tune to save her life. She can play the guitar well though, she should just stick to that instead of trying to sing.
Taylor Swift on the other hand actually has real talent and can't belt out some nice vocals and she writes a lot of her own lyrics/songs and also knows how to play the guitar and other instruments well. Plus Taylor is good at multiple genres of music and has won more prestigious awards than Katy.
So Taylor Swift wins this hands down. Don't even know how there could even be any question, the two shouldn't even be in the same category. It should be like Katy Perry vs Britney Spears, and Taylor Swift vs Lady Gaga - aka Auto Tune vs Auto Tune, Real Talent vs Real Talent.