I'm mostly going off places like Primavera/Pinkpop. She's got a pretty hefty discography, history with the festival and she is one of the most talked about artists this year. Add to that she's British and female, and it seems like a pretty safeish bet to me.
Maybe I'm a bit naive to Fred, because while I'm aware of him being 'massive', I only know one song and in my mind he doesn't have enough heft behind his popularity, if that makes sense.