You need good songwriting to craft good songs. The better your songs overall, the more willing people will be to see you live, providing the artist is a decent performer at the same time of course. So, I'd have to say songwriting, because that can lead to success in touring.
Depends what kind of artist you are. For Katy Perry, tours are more important, I think. For Taylor Swift, songwriting. A pop star performs, that's what they need to excel at. A singer-songwriter needs to write songs.
You once talked to me about love and you painted pictures of a never never land. And I could have gone to that place, but I didn't understand