Ke$ha and Lorde are at polar opposite ends of the spectrum in personality and music. If you had to make a choice between the two, as in you can only listen to one or the other's music, who would you pick? Would you go for serious Lorde or "doesn't take herself seriously" Ke$ha?
Kesha is a better vocalist, Lorde is a better songwriter.
All depends if you wanna listen to dance music or not..
I'd go with Kesha.
Lorde is a really brilliant songwriter, but I've listened to Pure Heroine a few times (which lets face it, is her discography) and she doesn't have anything as lyrically sound as Ke$ha's Past Lives.