Yorknew is my favourite HxH arc. It's very well written, extremely hype, not too long, quite entertaining. Great cast, the real MC of the manga Kurta Kurapika is there, the Troupe, namely Chrollo and Hisoka.
However, I think from a writing standpoint, CAA is superior. The characterization, developments, storytelling, themes, are all superior in CAA compared to Yorknew.
From Meruem, a typical ruthless tyrant who values power above all else, to the being he becomes at the end, his relationship with Komugi, Netero achieving his dream, Killua and Gon development, Pouf's development, to looking at humanity from a different perspective and the juxtaposition between Meruem and Gon, like when Gon realizes Kite has died, the moment is similar to when Meruem realizes Komugi is hurt. Yet while Meruem chooses to exhibit the best of humanity, to forgive and understand the other side, Gon descends into the darkness, becoming the animal he swore he would destroy. He feels nothing but pure hatred for Pitou, and gives up everything (his nen of course, but also his status as one who exhibits the best of humanity) to eradicate Pitou until nothing's left. The animal chooses to be human, and the human chooses to be animal; it's another ironic reversal, and it's one that compliments the CAA's own themes of showing humanity's potential to degrade itself.
The emotions as well
I still like Yorknew more though, but I think CAA is a superior arc. And like I've said above, I took what was usually perceived as the best arc, so CAA got the nod.