It's a bit unfair since Taylor has a couple more albums, but Taylor's lyrics and melodies both are superior. Even Katy's very best songs (TD, HH, TOY, Lost, DR) have 'good' lyrics while Taylor's best have AMAZING lyrics.
I saw Katy's TD and Prism tours and Tay's RED tour and I like them about equally there.
They both have some great music videos (BS, TOY, TD, Style
) but some bad ones too (WH, DH, Birthday), so they're about equal to me there too.
I don't think it makes sense to rate their 'personalities' since we don't know them personally, so when it comes to their public personas, I think that Taylor comes across as a bit more genuine and less competitive, which I like.